0965-LP-122-1010 Lorain Public Address system.pdf

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MANUAL: Lorain GAI-LPA Marine Public Address System Model D

AUTHORITY:

Supervisor of Shipbuilding Conversion and Repair, USN Ninth Naval District Sturgeon Bay, WI 54235

Ser 905 270:LEG:jmh Dated 4 A p r i l 1978 Ser 230jd105 d a t e d 12 J a n u a r y 1977 (Navsea #)

QUANTI TY QUANTITY

CONTRACT OR S H I P S OF OF BUILDING

PURCHASE ORDER APPLICABLE MANUALS EQUIPMENT YA3.D

N00024-76-C-2044 T-ATF 166-169 13 1 per ship MARTNETTE

MARINE

CORPORATION

P.O. 11230-159 Marinette, Wis cons in

NOTES:

DATE: June 22, 1978

CERTIFICATION :

I T I S HEREBY C E R T I F I E D THAT T H I S MANUAL TO BE PROVIDED UNDER

SHOWN ABOVE

CONTRACT N 0 0 0 2 4 - 7 6 - C - 2 0 V t HAS BEEN APPROVED BY APPEOVAL DATA

- 1 Vice Presi den;t../ General Manager

LORAIN GAI-LPA

PUBLIC ADDRESS SYSTEM

MODEL D

Page

LORAIN ELECTRONICS

SYSTEM DESCRIPTION

SPECIFICATIONS

OPTIONAL EQUIPMENT

UNIT WEIGHTS

INSTALLAT ION

WIRING

PRODUCTS WARRANTY

OPERATING INSTRUCT I O N S

MAINTENANCE INSTRUCTIONS

SYSTEM SET UP PROCEDURE

BOGEN - INSTALLATION & OPERATING MANUAL - MODEL MBT60

SCHEUATIC DIAGRAM - MODIFIED MBT60 AMPLIFIER

R2106 - 730 WEATHERPROOF STATION - OUTLINE AND MOUNTING DIMENSIONS

R2440 - MLQTC OUTLINE AND MOUNTING DIMENSIONS

R2114 - 702-2 ENCLOSURE - TYPE GAI-LPA MODELS - D - E

R2122 - GAI-LPA MODEL D - CONTROL UNIT - 901 - FLUSH MOUNT DETAIL

R2119 - LORAIN G A I - P A MODEL D - 700 STATION - 702 ENCLOSURF: WITH TRIM PLATE

R2115 - PH TRUMPET, I D - 60 DRIVER, SPEAKER MOUNT

SS-1853 - HAZARDOUS AREA SPEAKFB AMPLIFIER ASSEMBLY - MODEL 665 E - MOUNTING

ADDENDUM #1 (EXPLOSION PROOF SEAL OFF REQUIREIENT ) 0

DETAILS

DIAGRAM

SS-1854 - HAZARDOUS AREA SPEAKER AMPLIFIER ASSEMBLY - MODEL 665 E - WIRING

745-D - HAZARDOUS AREA WEATHERPROOF STATION - MODEL 745-A - MOUNTING DETAILS

E 5 3 5 - MODEL 1001 ( S P ) MASTER UNIT - HAZARDOUS AREA SPEAKER TALKBACK - DOME

SS-1865

SS-1867

SS-1869 - HAZARDOUS AREA WEATHERPROOF STATION - MODEL 745-A - MOUNTING DETAILS

SS-1871 - HAZARDOUS AREA CVEATHERPROOF STATION - MODEL 747-A - MOUNTING DETAILS

ADAJXT BULLETIN 973 - SECTION F6 - PARTS LIST FOR EXPLOSION PROOF SEAL OFF

DRILLING SHIP

- HAZARDOUS AREA STATION - MODEL 740A - MOUNTING DETAILS

- HAZARDOUS AREA. STATION - MODEL 7428 - MOUNTING DETAILS

R2118 - R2111 -a112 -a 3 9 1 - E113 - R2120 - R2121 - R2315 - R2528 -

GAI-LPA - PRE-AME'LE AND POWER AMPLIFIER P.C. BOARDS AND POVJER SUPPLY

PILOTHOUSE MASTER CONTROL - AMPLIFIER,

TYPE GAI-LPA MODEL D

730 FEMITE STATION - AMPLIFIER,

745-D REIKITE STATION - EXPLOSION PROOF - GAI-LPA MODEL D

BLOCK DIAGRAM TYPE GAI-LPA MODEL D

TYPICAL CABLF: CONNECTIONS - TYPE GAI-LPA MODEL D

MASTER CONTROL CABLE - TYPE GAI-LPAMODEL D

BLOCK DIAGRAM - TYPE GAI-LPA MODEL D - TUG CABLING

GAI-LPA MODEL D - CONTROL UNIT-901 - SURFACE MOUNT DETAIL

ENCLOSURE AND CONTROL UNIT -

ENCLOSURE AND SPEAKER - TYPE GAI-LPA

MODEL D

a

LORAIN GAI-LPA

PUBLIC ADDRESS SYSTEM

MODEL D

SYSTEM DESCRIPTION

This completely transistorized public address system permits voice communication between two or more locations by any of three methods, and under extreme noise conditions.

Basically, each station consists of a combination handset/speaker amplifier, a handset with a dynamic noise cancelling microphone, and a loudspeaker. The handset/speaker amplifier is a plug-in unit mounted in either a cast aluminum watertight enclosure for exposed locations, or a formed sheet metal enclosure for protected areas. Loudspeakers are com-pletely submergence and weatherproof.

The three modes of operation are:

1. "PACE" - in which any station calling will be heard on the loudspeaker of all other stations.

making announcements or in alerting a particular station or person, who can then communicate via the "PARTY" c hanne 1.

Used in

2. "PARTY" - in which only the called and calling party converse by means of the handsets. The use of a noise cancelling microphone permits excellent voice communi-cation under severe ambient noise conditions. "PAGE" and "PARTY" are available from any station to any other station. In systems of four or more stations, two inde-pendent conversations can be carried on simultaneously -one on each channel.

3 . "SPEAKER TALKBACK" - If instructed to do so by the "Master Control" station, a remote station can set up "SPEAKER TALKBACK" by operating momentarily a push button, after which hands free talkback over the loud-speaker can be carried on between the remote and the Master under the control of the Master station.

SPECIFICATIONS

NO. 701 - HANDSET/SPEAKER AMPLIFIER (Prints R-2112/R-2118)

Power Requirement - Voltage - 105/130 Volts AC 50/60 Ht

Current - No signal - 5 Watts Maximum signal - 29 Watts

Temperature Range - -3OOC to +7OoC

Finish - Light grey enamel baked on Zinc Chromate Dimensions - 8-1/8" X 8-1/8" X 3" behind panel (overall)

3-1/2" in front of panel (overall)

HANDSET AMPLIFIER SECTION

Input Impedance - 10 ohms output - 1.5 Volts into a 33 o h load

Controls - Transmitter Level - accessible through side. a Receiver Volume - accessible through side.

Frequency Attenuation - accessible through side.

Handset Transmitter - 10 ohms noise cancelling dynamic Handset Receiver - 130 ohms high efficiency

SPEAKER AMPLIFIER SECTION

Input Impedance - 10,000 ohms (bridging)

Output Impedance - 8 or 16 ohms

Output Power - 12 Watts at less than 5% distortion Frequency Response - 250 to 15,000 Ht (can be attenuated to 2400 Hz)

Controls - Speaker Volume - control accessible behind nameplate on front panel.

- Frequency - control accessible through side bracket.

NO. 732 WEATHERPROOF ENCLOSURE (Print R-2106)

Construction - Sand Cast Aluminum Alloy Cam Type Latch Hinged Door with Neoprene Gasket

Finish - Double coat aluminum paint

Mounting - 4 Mounting lugs with 7/16" diameter holes

ConduitlCable - Enclosure has one hubplate at top with 1/2" pipe thread, one hubplate at bottom with 1-1/4" pipe thread. Supplied with

I neoprene gaskets and stainless steel bolts.

I

Wiring I - Barrier type terminal strips with fiberglass I covered plastic coated wiring. Self aligning plug with gold plated contacts for plug-in amplifier. Hermetically sealed relays.

Dimensions - 10-5!8" wide X 14-7/8" high X 9-5/8" deep (overall)

NO. 1001 W T E R CONTROL STATION (Prints R-2111/R-2118)

NO. 712 HANDSET/SPEAKER AMPLIFIER

Same electrical specifications as #701 amplifier except handset and hookswitch not a part of unit.

NO. 702-2 ENCLOSURE (Print R-2114)

Construction - Heavy guage steel with two 3/4" - 1" knockouts at each end.

rear panel.

Four 5/16" mounting holes in

Finish - Light grey baked enamel on Zinc Chromate.

Dimensions - 16-1/4" wide X 8-1/8" high X 5-1/4" deep (overall)

Power Supply - Control circuits (Print R-2111) 28 Volts DC (nominal) at 1-1/2 amperes for relays and panel lamps.

NO. 901 CONTROL UNIT (Print R-2122)

Construction - Mounting panel of 1/8" aluminum with 1/16" phenolic engraved overlay. Protective cover of #PO guage steel with light grey enamel finish.

J

Controls - Handset with push-to-talk switch in handle, handset hanger with hookswitch, illuminated four push button switch for channel selection and a three way toggle switch for control of illumination.

Dimensions - 10" high X 4-1/2" wide X 4-1/8" deep (overall) behind panel approximately 4-1/2" (overall) in front of panel with handset.

OPTIONAL EQUIPMENT

TRUMPET ROOF SPEAKER (Print R-2 115)

Speaker - University PH Trumpet supplied with ID-60 driver unit.

Impedance - 16 ohms

Input Power - 60 Watts Mounting - Carlisle-Pinch cast brass searchlight mount with stainless a steel speaker horn mounting bracket.

horizontal movement, with locking device and automatic stops.

Capable of 360'

Dimensions - 34-1/8" above deck (overall) 20-1/2" length of horn and driver

BOOSTER AMPLIFIER (Bogen MBT-60)

See Bogen instruction book for description.

Dimensions - 13-1/2" long X 8" wide X 7" high (overall)

UNIT WEIGHTS

701 Amplifier - 7 lbs. net 712 Amplifier - 6 lbs. net 732 Enclosure - 17 lbs. net HM2-ST Speaker - 7 lbs. net 702-2 Enclosure - 18-1/2 lbs. net with power supply 901 Control Unit - 5-1/4 lbs. net MBT-60 - 22 lbs. net PH Trumpet w/lD-60 and Mounting - 29 lbs. net

INSTALLATION

(Refer to Block Diagram R-2113)

The system is composed of a #lo01 Pilothouse Waster Control" and a number of P730 Remote Stations and associated speakers.

conductor) cable is required between all stations.

cable I s needed between remote station and its associated speaker. Recom-mended cable is IEEE-45, Types TT-TIA-6 & TT-TIA-2. This is aluminum armored paired #16 conductor, approved for shipboard installation.

MOUNTING 8730 REMOTE STATION (Print R-2106)

A six-pair (12 A two-pair (4 conductor)

Enclosure should be bulkhead mounted at a height of not over 60" for convenient use of the handset. The associated speaker is also used for talkback, and should be located so that the user is not over five to six feet from speaker in normal operation.

The weatherproof enclosure (P732) has a 85406 hubplate on the bottom, threaded for 1-1/4" pipe.

diameter of .88". Suitable watertight cable connectors and reducers must be supplied for cable entry.

thread.

side for cable connectors (connectors not supplied). The recommended two-pair cable between the #732 enclosure and the speaker I s approximately .64" in diameter.

The recommended six-pair cable has an outside

The top hubplate is a #5435 with a 1/2" pipe The MM-2-ST speaker has two tapped 1/2" pipe thread holes on either

Care must be used to seal cable into connectors to prevent water seepage between outer armor and underlying cable covering.

use of G.E. Aluminum Silicone Construction Sealant #SE-1209. It is not essential that cable armor be grounded to enclosure through the cable connector.

We suggest

INTERCONNECTING CABLE (Print R-2120) (Recommended TT-TIA-6 6 TT-TIA-2)

A six-pair (twisted pair, 12 conductor) armored cable of not less than #16 size wire should be used. All stations are connected in parallel, so wiring is comparatively simple.

the pilothouse area and runs to each remote station by the most expeditious route. Junction boxes (not supplied) can be used to branch off from fore and aft cable runs to the various remote stations. Junction boxes should provide twelve terminals for cable connections and be approved watertight units. Cable can be spliced if necessary, but would make trouble-shooting more difficult in case of future cable trouble. Maintain color code throughout entire system.

Cable starts from the #702-2 enclosure in

POWER SOURCE

System uses 115 :Volts AC, 60 cycle power. This should be supplied I I

( 5 1

0 from the same power panel as the other pilothouse electrical equipment through an independent breaker or fused switch of not over 10 amp capacity.

The supply line can be connected to the system at the nearest junction box or to the P702-2 enclosure if more convenient.

and using very little standby power, it is not anticipated that the system will normally be turned off except for maintenance.

Being 100% transistorized

PILOTHOUSE CONTROL UNIT #lo01 (Prints R-2114 & R-2122)

The #702-2 enclosure should be mounted in a protected space as con-veniently close to the #SO1 control unit as possible.

(Print R-2114) has four 3/4" - 1" knockouts for cable entry.

entering enclosure are:

The enclosure Cables

1. Six pair from remte stations.

2. Control cable (20 conductor) Belden #8775 or equivalent.

Cable supplied by vendor if advised of the required length.

3. Two pair to booster power amplifier (MBT-60).

4. One or two pair to pilo,thouse speaker.

Enclosure should be mounted on a vertical bulkhead or surface convenient to cable entry and with sufficient space to enable easy access for wiring and repair if necessary. It should not be subject to weather or extreme temper-atures.

a The #901 control unit (R-2122) is designed for flush mounting in a control console for vessel operating controls.

can be supplied if requested.

Bulkhead or surface mountings

The MBT-60 booster power amplifier is 13-1/2" long X 8" wide X 7" high.

It should also be mounted in a protected area, possibly near the 8702-2 enclosure for easy access and wiring.

ROOF SPEAKER PH/fBT-60 (Print R-2115) type pedestal allowing 360' rotation of the speaker in. the horizontal direction only. It should be mounted on the pilothouse roof at a point allowing con-venient operation from the inside of the pilothouse and unobstructed coverage from the speaker. If the pedestal mount is too low for proper speaker clearance, it can be raised by a section of 9'' or 10" diameter pipe of proper height welded to the deck with a plate on top for pedestal. The brass tube shaft can be cut and extended to required length by inserting a 5 / 8 " diameter brass rod of the proper length.

This unit consists of a reflex trumpet speaker mounted on a searchlight

Cable from amplifier to speaker can be brought through a bushing in the base of the pedestal or through the deck, and terminated in a junction box at the base of the pedestal. A floating stop is provided to prevent continuous 0

( 6 ) rotation of the speaker.

cable must be provided to connect from the junction box to the driver of speaker and allow 360' rotation.

Sufficient flexible neoprene covered C18 or larger

WIRING

Typical cable and equipment terminations are shown in print R-2120.

Watertight entrance bushings (not supplied) must be used on all equipment in exposed areas, and precautions must be taken to seal the cable to prevent water seepage between armor and the inner cable cover. Cable runs should be made in an approved manner with due regard for mechanical protection.

junction boxes are required for branch circuits, they should be watertight, of a size sufficient for the number of cables entering, and supplied with a barrier type terminal strip of at least 12 terminals.

If

The use of solderless insulated spade lugs is suggested. Barrier strips in all equipment8 use a #6 terminal screw and lugs should be for this size terminal screw and for the wire size of cable supplied.

Uniform color code should be followed in all wiring and care taken - not to break up pairing when terminating.

A special cable (Belden 8775) between the 702-2 enclosure and the 901 control unit can be supplied by Lorain Electronics (already made up and lugged) when advised of the required length.

A protective insulating spray coating should be applied to remote station terminal strips after wiring is completed. Great care must be used to prevent spray from reaching socket into which amplifier is plugged.

OPERATING INSTRUCTIONS

REMOTE STATIONS (No. 730 Weatherproof)

This unit is housed in a cast aluminum enclosure with a gasketed, hinged cover. Open cover by turning locking handle counter-clockwise. When closing cover, push in lightly and turn locking handle in clockwise direction.

Opening the cover discloses a panel on the left side of which is a handset and hookswitch hanger; on the right side - a black push button marked "PUSH FOR PAGE - RELEASE TO PARTY". At the lower center of the enclosure is a red push button marked "PUSH FOR SPEAKER TALKBACK".

Mounted nearby is a weatherproof loudspeaker with a red indicator light in the center of the junction box below the speaker opening.

INITIATING A CALL ON "PAGE"

Remove handset from hanger, push firmly the black button marked "PUSH TO PAGE" and speak clearly into handset transmitter while depressing button. (Be sure button is in the vertical position.)

to communicate. As soon-as you finish speaking, release button and wait for other party or station to answer.

heard on the loudspeakers at all the other stations. When the called party answers, you will hear him on the handset receiver.

Releasing the button places you on the "PARTY" channel.

(See following. )

Announce the person or station with which you wish

Your call will be

ANSWERING A CALL OR CONVERSING ON "PARTY"

When you hear a call on your loudspeaker, open the enclosure, You are remove handset from hanger and talk into the transmitter (be sure black "PUSH TO PAGE" button is in the vertical position).

automatically on the "PARTY" channel and you converse with the other party as on any telephone. This conversation is not heard on any speaker, conversations are normally carried on tn the "PARTY" position. With

All calls &st be initiated in the "PAGE" position, but two stations using the "PARTY" channel, all other stations may still use the "PAGE" channel.

USING "PAGE" CHANNEL FOR TWO-WAY TALKING

In the event that two stations are using the "PARTY" channel, all other stations are available on the "PAGE" channel. A second conversation can be carried on between two stations using the "PAGE" channel by the calling party instructing the called party to answer in the "PAGE" position. To facilitate a conversation in this position, turn the black "PUSH TO PAGE" button 1/4 turn clockwise, which locks it into the "PAGE" position.

speakers, only on the handsets. Return the buttons to the vertical position when call is completed. I

0 You will not hear this conversation on the

(8)

USE OF "SPEAKER TALKBACK"

This is only to be used between the "Master" station and a remote station. A remote station is normally called on the "PAGE" channel by the "Master" station, who instructs the remote operator to answer on "SPEAKER TALKBACK". The remote operator answers by momentarily depressing the red button in the lower center of the enclosure and observing if the indicator lamp in the front cover of the associated loudspeaker lights up, system is set up for "SPEAKER TALKBACK" and the operator needs only t o talk towards the loudspeaker thereafter until the "Master" station releases by hanging up.

will depend on the ambient noise level and the distance of the talking party from the loudspeaker. With fairly low background noise, satisfactory conversation can be carried on when talking in a normal voice from 10 to 15 feet from the loudspeaker. The voice should be directed toward the speaker for best results.

This indicates that the

Satisfactory "SPEAKER TALKBACK"

GENERAL

Each of the three channels "PAGE", "PARTY", and "SPEAKER TALKBACK" are common to all stations. Thus, more than two stations can converse on each channel if desired. NOTE: In "SPEAKER TALKBACK" the 'Master" station can talk to several remote stations and they can talk back to the "Master", but one remote cannot talk to another remote.

MASTER CONTROL STATION (#sol)

The 'Master" control consists of a handset and a hanger with spring retainer, an illuminated four push button selector switch and a three position toggle switch to control push button illumination, TO INITIATE A CALL

Remove handset from hanger by pushing up or forward to release from spring clips. Push down the selector button marked "PAGE" so that it locks, press the black bar switch in the center of the handset and make the announcement in a clear voice, talking into the transmitter at a distance of not more than two to three inches. Release the handset switch as soon as you finish talking and immediately push down the selector button marked "PARTY" and wait for the called station or person to answer. They will normally answer on the "PARTY" channel unless you instruct them otherwise.

ANSWERING OR CONVERSING ON "PARTY"

When answering a call from a remote station, remove handset -and push down the "PARTY" selector button.

talk bar on the handset when you talk and release to listen.

You must push the

USING "PAGE" FOR TWO-WAY TALKING

In the event that two or more remote stations are usinn the "PARTY" channel, you may still "PAGE" all stations on tie loudspeakers. If you wish to talk to a station while "PARTY" channel is busy, request the called party to answer on "PAGE".

You remain with the "PAGE" selector button down.

USE OF "SPEAKER TALKBACK"

Remote stations may be requested to answer directly on

"SPEAKER TALKBACK".

remote station to go to "SPEAKER TALKBACK", then change selector buttons from "PAGE" to "SPEAKER TALKBACK" as soon as your announcement is completed.

station complying with your request by the presence of background noise in your handset and speaker.

as before.

loudspeaker.

restores the remote station to standby on "PAGE".)

Initiate the call on "PAGE", direct the

You will be aware of the remate

You operate by push-to-talk The remote operator replies by talking toward his

(Replacing your handset in the hanger automatically

USING ''ROOF SPEAKER"

If it is desired to direct orders to a man on the dock or at a distance from the pilothouse, the roof speaker may be used by removing the handset, pushing the "ROOF SPEAKER" selector button, wait about two seconds and then proceed with normal push-to-talk use of the handset.

be projected over a trumpet type speaker on a searchlight mount on the pilothouse roof. The control handle should be adjusted so that it is pointing in the direction you wish to talk. This speaker has sufficient power to be heard several thousand feet under normal conditions.

Your voice will now

ILLUMINATION

A three position toggle switch is located just below the push button selectors. Operation to the left gives full illumination;

to the right gives low illumination, center is OFF.

is normally all that is required.

Low illumination

GENERAL

1. Initiate calls on "PAGE" and switch to "PARTY" for reply under normal operation.

2. General calls can be made on "PAGE1' at all times, even if "PARTY" channel is in use by several remote stations.

3. Replace handset in hanger, especially after using "SPEAKER TALKBACK", as this automatically restores any remote stations that were locked up on this channel.

4, The speaker associated with t h i s s t a t ion has a volume control knob i n the center of the cover below the speaker opening. This can be used t o adjust t o the desired speaker level.

5. When using "ROOF SPEAKER", operating the selector button supplies power t o the booster amplifier, but i t requires about two seconds for capacitors to charge before full output can be obtained.

button ahuts off power t o booster.

Release of selector

6. Replacing handset automatically restores any selector button tha t w a s operated and resumes monitoring of the "PAGE" channel.

MAINTAINANCE INSTRUCTIONS

Repairs should be performed by competent technicians familiar with transistor circuits. Vacuum tube or transistorized meters should be used for all testing.

Failure of any single unit should not affect the operation of the No maintainance is required except to keep other units in the system.

equipment clean and a routine check for mechanical damage to handsets or coiled cords.

The following checks can be made in the event of a failure:

1. No Receiver Audio - Receiver should have a DC resistance of about 35 ohms - Replace if open or shorted.

2. No Transmitter Audio - Transmitter should have a DC resistance of 6 to 9 ohms - Replace if open or shorted.

3. Station Completely Dead - Remove plug-in amplifier and check fuse (use continuity check) - Replace with proper size (refer to circuit diagram).

DO NOT OVERFUSE.

4. If Fuse is OK

5. No Speaker Audio

- Check across terminals 1 & 2 of enclosure terminal board with AC voltmeter on the 150 Volt scale.

check main supply source and cable connections.

If voltage is present, replace amplifier with a spare unit or have defective one repaired by authorized personnel.

If voltage not present,

- Remove cover on junction box below speaker opening, remove one wire from either of the two right hand terminals on the four terminal strip. Check speaker with ohmmeter, it should have a DC resistance of 10 to 12 ohms. Replace speaker unit if open or shorted, If speaker is OK, check wiring to amplifier enclosure.

If pilot lamp in speaker junction box does not light when in "SPEAKER TALKBACK", unscrew red jewel and remove bayonet base lamp. Check.

Replace if defective. If lamp is OK, check wiring to amplifier enclosure.

EXPLOSION PROOF STATION

74 5

Remote S ta t ion (745 Explosion Proof ) 648C subset.

The 648C subset is housed in c a s t aluminum enclosure w i t h a gasketed hinged cover. Open the cover by turning handle counter clockwise.

Inside will be a handset, a hook-switch and a black button d i r ec t ly under t h e c rad le of the hook-switch.

and push t o s e t up speaker talkback.

T h i s black button is used f o r paging

I n i t i a t e a Cal l on Page

L i f t handset, depress t h i s black button and hold i n while announcing i n handset the message and s t a t ion you a re ca l l ing .

a s soon a s you are f in i shed with your page and wait f o r par ty t o answer.

Releasing t h i s button puts you i n par ty pos i t ion and a s soon a s the paged pa r ty answers h i s voice w i l l come out of the handset.

Release this black button

Answering a Cal l o r Conversing on Party

When you hear a c a l l on your loudspeaker, open enclosure, remove hand-s e t from hanger and t a l k i n t o transmitter. The two s t a t i o n s a r e automatically on pa r ty a s long a s the page button is not depressed.

Using Page Channel f o r Two Way Talking

In t h e event t h a t 2 s t a t ions a r e using par ty channels, two other explosion proof s t a t i o n s can t a l k on page channel.

page button depressed during talking and receiving. The audio will be coming out of t he handset instead of the speaker.

Both p a r t y ' s have t o keep the

Use of Speaker Talkback

Speaker talkback can only be used between master s t a t i o n s and remote s t a t ions , and remote s t a t ions t o master. Not between s t a t ions .

The P i l o t House and remote s t a t i o n a re normally ca l led by page mode.

After contact has been made, e i the r s t a t ion or P i l o t House can request speaker talkback.

control marked Speaker Talkback f i r s t then remote s t a t i o n depresses black button under handset cradle momentarily unti l r e l a y locks. They a re then i n Speaker Talkback mode.

and s t a t i o n hang up handsets.

After request i s made P i l o t House must depress button on Master

Both systems r e tu rn t o normal when master control

I n a mixed system where non explosion proof and explosion proof ex is t , the operating ins t ruc t ions f o r the explosion proof s t a t i o n will be used with explosion proof s t a t ions . The operating ins t ruc t ions f o r the non explosion proof standard 730 and 700 s t a t ions will be the standard operating instruc-t ions.

EXPLOSION PROOF MASTER

MODEL GAI-LPA MODEL D/EX

The un i t is housed i n a cas t aluminum box with a gasketed hinged cover.

Open door by turning handle counter-clockwise.

On t h i s model i t may be noted t h a t the function selector i s of the ro ta ry type.

It w i l l a l s o be noted t h a t t h e handset i s not of the Push-to-Talk type. Push-to Talk and release-to-listen i s accomplished by the black button located under the handset hang up.

t o t a l k and released t o l i s t e n .

fea ture .

T h i s i s assessable by removing the handset. This button is pushed T h i s button i s used also f o r Speaker Talk-Back

I n i t i a t e a Call on Page

Remove handset, s e t s e l ec to r switch t o Page, depress and hold i n black button Release black under hoodswitch and announce message by speaking i n t o transmitter.

button and wait for answer.

i s desired t o t a l k from t h i s s t a t i o n and released t o l i s t e n .

This black button has t o be depressed each time it

Conversing on Party

This function i s requested by Party ca l l i ng .

ro ta ry switch on t h i s master 5s rotated t o Party posit ion.

i s depressed f o r Talk and released t o l i s t e n .

To s e t up t h i s function the 0 Again, the black button

Use of Speaker Talk-Back

Speaker Talk-Back can only be used between master s t a t i o n and remote, o r remote t o master s t a t ion . Not Between Stat ions.

After contact has been made by both p a r t i e s , a request may be made f o r speaker Talk-Back by remote s t a t i o n f o r hands f r e e operation.

will s e t h i s Rotary Selector t o Speaker Talk-Back, press the black button under hookswitch, remote s t a t i o n then pushes i n h i s Speaker Talk-Back switch once t o energize relay. The remote s t a t i o n i s now on Speaker Talk-Back, speaking towards and receiving out of speaker. The Pilothouse must depress h i s black button under hookswitch i f he des i res t o t a l k and must re lease it t o l i s t e n .

A t request, t he pilothouse

The system rever t s t o Page condition when Pilothouse hangs up handset i n hoodswitch.

MASTER CONTROL

Same checks can be made as noted above for the amplifier, handset and speaker. In addition, check the following:

If no illumination of any push buttons on control unit, check fuse in DC power supply in left side of amplifier en-closure. If fuse is OK, check for DC (28 Volts) across terminals 3 & 4 of power supply.

is no DC, have unit serviced by competent technician.

If fuse is OK, but there

If any push button does not light up, remove push button cover by pulling up. Miniature lamp is held in a clip, carefully remove and replace with new lamp of the same type. Replace cover.

BOOSTER AMPLIFIER

If there is no audio from the Roof Speaker when this channel is selected from the control unit, check for power by the pilot light indication on front of booster amplifier.

breaker (red button). Push in to reset. If this does not restore operation, have it checked by a competent technician.

Unit is provided with circuit

ROOF SPEAKER

If the booster amplifier appears OK, but there is no audio from the speaker, open the junction box on the pilothouse roof and remove one wire coming from the amplifier. Check for DC resistance to the speaker driver; it should be 6 to 8 ohms. If open or shorted, check driver unit itself. If driver is OK, the flexible cable from driver to junction box is probably open and should be replaced.

is open or shorted, it should be replaced.

If driver

REPLACEMENT PARTS

Parts lists appear on the appropriate prints for the various units. Lorain Electronics Corporation stocks spare parts or sub assemblies for all unitr. Competent technicians are available at our factory and at various ports on the Great Lakes and Inland Rivers.

' 0

. G A I - LPA - MODEL I'D"

SYSTEM SET UP PROCEDURE

1) A f t e r i n s t a l l a t i o n and a l l w i r i n g is completed, remove a m p l i f i e r s from master and a l l remote s t a t i o n s ( i f a l r e a d y i n p l a c e ) .

2) With a m u l t i m e t e r (Simpson 2 6 0 o r s i m i l a r ) make t h e fo l lowing s t a t i c checks on master s t a t i o n :

a ) S e t ohms t o X 10,000 scale , ground one l e a d of meter. One TB2 of 702-2 e n c l o s u r e of master, check a l l t e r m i n a l s 1 t h r u 11. Should show a minimum of 2 0 , 0 0 0 ohms t o ground except 3 which i s ground.

b ) S e t ohms t o X 1 scale. On TB2 check fo l lowing:

Between 1 and 2 should b e approximately 5 ohms

I 1 11 50 ohms Between 4 and 5 I '

I ' ohms Between 6 and 7 ' I ohms Between 8 and 9 Between 10 and 11 should b e a s h o r t .

I I

I f

I I

1 1

3) Apply AC power t o system.

On TB-2 of 702-2 e n c l o s u r e of master make f o l l o w i n g checks:

a ) S e t meter f o r 250V AC scale and check f o r 115 AC on / f l and 2 .

b ) S e t meter f o r 50V D C , neg. l e a d t o # 3 . Check f o r 28V DC on 1\10 and 11.

Remove handse t on Master C o n t r o l , o p e r a t e Speaker Talk Back b u t t o n on master and p u t a temporary jumper between /I4 and # 7 on TB1 i n a 702-2. TB2 term # l o should now show z e r o v o l t s .

4 ) With AC power s t i l l s u p p l i e d and Master set up as i n (b) above, make fo l lowing checks on T B 1 i n a l l remote s t a t i o n c a b i n e t s .

a ) Meter on 250 AC s c a l e , check f o r AC on #1 and 8 2 .

b) With meter on X1 ohms scale , check r e s i s t a n c e a c r o s s t e r m i n a l s 1/8 and 9 , # l o and 11, 1/12 and 13.

I f n o t , check f o r improper connec t ions .

With meter on 50V DC scale and neg. l e a d on 113, check f o r + 2 8 v o l t s on f 1 5 and z e r o v o l t s on # 1 4 .

Should be approximately 50 ohms f o r each pair .

c )

5 ) Before r e p l a c i n g t h e h a n d s e t / s p e a k e r a m p l i f i e r u n i t s i n t h e remote s t a t i o n e n c l o s u r e s , d i s c o n n e c t t h e AC supply t p t h e system 'and check t h e f o l l o w i n g p r e l i m i n a r y ad jus tment of t h e v a r i o u s c o n t r o l s on each a m p l i f i e r u n i t .

a ) With t h e f r o n t p a n e l f a c i n g you and t h e connec tor p lug on t h e rear p a n e l a t t h e t o p , l o c a t e on t h e r i g h t hand s i d e p a n e l a name p l a t e marked "Handset" w i t h t h r e e screw d r i v e r c o n t r o l s d e s i g n a t e d from t o p down as of h a n d s e t and should b e about 118 t u r n c o u n t e r c lockwise from f u l l on.

"Rcvr" c o n t r o l sets r e c e i v e r volume and should b e approximately 114 t o 112 t u r n counterc lockwise from f u l l on. "Freq" c o n t r o l u s u a l l y can b e f u l l y counterc lockwise .

" X m t r " - "Rcvr." - "Freq." " X m t r " c o n t r o l sets o u t p u t

-2-b ) On t h e l e f t hand s i d e p a n e l is a c o n t r o l marked "Spkr Freq".

a d j u s t s t h e h i g h frequency response of t h e s p e a k e r a m p l i f i e r and can b e set a t approximately mid-range.

On t h e f r o n t p a n e l i s a name p l a t e "Gai-Tronics" s e c u r e d by two small screws. Loosen t h e r i g h t hand screw and r o t a t e name p l a t e r e v e a l i n g t h e screw d r i v e r ad jus tment f o r s p e a k e r volume. P r e l i m i n a r y s e t t i n g should b e about midway of c o n t r o l . The f i n a l ad jus tment can b e made a f t e r a m p l i f i e r is i n s t a l l e d .

T h i s c )

d) A l l a m p l i f i e r u n i t s can now b e i n s t a l l e d i n c a b i n e t s b e i n g s u r e t h a t p l u g and s o c k e t connec tors mate p r o p e r l y w i t h s u f f i c i e n t c o n t a c t w i t h o u t undue p r e s s u r e .

6 ) The a m p l i f i e r u n i t f o r t h e Master s t a t i o n i s b a s i c a l l y similar t o t h e remote a m p l i f i e r s except f o r no h a n d s e t o r push-button. A l l t h e ad jus tments are t h e same as i n (5) above e x c e p t f o r t h e receiver volume c o n t r o l which i s l o c a t e d behind a cover marked "Receiver Volume" on f r o n t p a n e l o f a m p l i f i e r .

should b e set a t about 114 t o 112 t u & c lockwise .

when i n f u l l o p e r a t i o n .

# 7 on T B 1 b e f o r e i n s t a l l i n g t h e a m p l i f i e r i n t h e 702-2 c a b i n e t .

T h i s F i n a l l eve l t o b e a d j u s t e d

Remove t h e temporary jumper between terminals #4 and

7) F i n a l check-out w i l l r e q u i r e a t least two people , one a t Master C o n t r o l and one t o check each remote w i t h master.

f 0 l lows :

Apply power t o t h e system and proceed as a ) Master o p e r a t o r removes h a n d s e t and p r e s s e s "Page" b u t t o n , t h e n p r e s s e s push b a r on handse t and pages i n normal v o i c e , r e l e a s i n g push b a r t o l i s t e n . Remote o p e r a t o r responds by removing h i s handse t and o p e r a t i n g "Push t o Page" b u t t o n on f r o n t p a n e l of a m p l i f i e r w h i l e speaking.

Speaker l e v e l can b e r e a d j u s t e d a t t h i s t i m e i f r e q u i r e d .

b ) Master o p e r a t o r w h i l e s t i l l on "Page" i n s t r u c t s remote t o go t o "Party" and t h e n p r e s s e s "Party" b u t t o n . Master and remote o p e r a t o r s should now b e a b l e t o converse wi th Master o p e r a t i n g push b a r w h i l e t a l k i n g and r e l e a s i n g t o l i s t e n . Speaker a t Master i s i n u s e i n a l l modes w h i l e l i s t e n i n g . A t t h e remote s t a t i o n t h e o p e r a t i o n i s t h e same as a r e g u l a r t e l e p h o n e , no b u t t o n s t o push and speech i s on r e c e i v e r i n handse t o n l y , s p e a k e r a t remote i s s i l e n t .

handse t .

Master i n s t r u c t s remote o p e r a t o r t o r e p l a c e

I t c ) Master o p e r a t o r pushes T a l k Back" then immediately pushes "Speaker Talk Back" b u t t o n . Remote o p e r a t o r (wi th handse t hung up) pushes t h e r e d "Push f o r Speaker Talkback" b u t t o n i n c a b i n e t below t h e a m p l i f i e r . The r e d lamp on s p e a k e r should now l i g h t i n d i c a t i n g u n i t i s connected f o r t h i s mode. Remote o p e r a t o r w i l l now b e a b l e t o converse w i t h Master by d i r e c t i n g h i s speech toward t h e speaker from a d i s t a n c e of 8 t o 10 f t . Master c o n t r o l s c o n v e r s a t i o n by u s e of push b a r on h i s h a n d s e t .

Page" b u t t o w a n d r e q u e s t s remote t o u s e Speaker

d) Each remote s t a t i o n should b e checked w i t h Master u s i n g above procedure.

e ) A s a f i n a l check, remote s t a t i o n t o remote s t a t i o n check should b e made u s i n g t h e "Page" and "Party" modes.

between remote s t a t i o n s , o n l y t o Master.

Speaker T a l k Back i s n o t p o s s i b l e

BOGEN

MODEL M B T 6 0

60 WATT

ALL-SILICON TRANSISTOR

BOOSTER AMPLIFIER

W L E A R BOGEN COMMUNICATlONS DIVISION

P . O . B O X 500

PARAMUS, N . J . 07652

INSTALLATION AND OPERATING MANUAL

R E A D T H O R O U G H L Y B E F O R E O P E R A T I N G E Q U I P M E N T

D ESCRI PTI 0 N

The Bogen model MBT60 is an all silicon tran-sistor booster amplifier designed to provide a power output of 60 watts for a quality sound reinforcement system. The amplifier can be used with any public address amplifier or preamplifier which can provide a 0.15 volt signal across 100,000 ohms at i t s out-put terminals.

The MBT60 boosts area coverage, provides in-creased reserve power and overcomes high noise con-ditions. It is excellent for u s e in auditoriums, in-dustrial plants, schools and all other areas where maximum coverage is required. Th i s high quality amplifier has exceptional power handling ability over the entire range of audio frequencies and ample power reserve to overcome high ambient noise conditions.

The MBT60 h a s provision for high impedance inputs a t 100,000 ohms, low impedance inputs (with plug-in transformers) a t 500/600 ohms and bridging inputs a t 10,000 ohms. A Speech-Music switch pro-vides optimum speech response. A floating balanced speaker output impedance of 8, and 16 ohms is pro-vided, a s well a s constant voltage outputs of 25 volts (2.6 ohms) C.T., 25 volts (10.4 ohms), and 70 volts (82 ohms) balanced or unbalanced. These outputs eliminate speaker matching problems when unequal amounts of power are required for various speakers of a distribution system. Remote volume control and remote standby control are provided with the u s e of a plug-in accessory.

T h e sol id s t a t e components are carefully operated well within the manufacturer's specifications to assure long dependable service. Components are rated for operating conditions far in excess of any likely to be encountered during normal use. Th i s unit, l ike all Bogen products, reflects a 34 year tradition of leader-ship in the electronic field. It represents the most advanced design and the highest standards of quality.

The unit is temperature s tab le and will function satisfactorily at full rated output between - 4 ° F (-20°C) and t158"F (t7O"C).

SPECIFICATIONS

POWER OUTPUT: 60 watts rms HARMONIC DISTORTION: L e s s than 3% a t 60 watts PEAK POWER: 110 watts FREQUENCY RESPONSE: 21 db from 12 Hz (cps) to 20 kHz (kc) POWER RESPONSE: 60 watts 22 db a t l e s s than

5% distortion from 40 to 10,000 Hz (cps)

GAIN: 85 db (High Impedance) HUM: -78 db below rated output DAMPING FACTOR: .Better than 51 REGULATION: Better than 3 db from no load to

SENSlTlV ITY (for rated output):

full load , High impedance input: 0.15 volt;

Low impedance: balanced input with TL600

0.04 volt; with TL10K 0.1 volt.

INPUTS:

High impedance: 100,000 ohms;

Low impedance: (with TL600 transformer) 500/600 ohms; bridging (with TL10K trans-former) 10,000 ohms

OUTPUTS: 8, 16 ohms, 25 volts C.T. balanced (2.6 ohms), 25 volts balanced (10.4 ohms), 70 volts balanced (82 ohms)

CONTROLS and INDICATORS: Power switch, power on indicator, volume preset, m u s i c speech filter switch to 125 VAC, 115 watts, 50-60 Hz (cps) POWER REQUIREMENTS (for rated output): 105

SEMI-CONDUCTOR 5: 7 Silicon transistors , 1 Zener diode, 4 Silicon diodes, 2 Germanium diodes.

DIMENSIONS: 8" wide x 13" deep x 5%'' high WEIGHT: 22 lbs,

- L -

U N P ACKlN G 0 T h e unit was carefully checked before leaving the factory. Inspect shipping container and amplifier carefully for indications of improper handling in ship-ment. If unit h a s been damaged, make an immediate claim to the dealer or distributor from whom i t was purchased. If unit was shipped to you, notify trans-portation company without delay and f i le a claim.

I

CONNECTIONS BETWEEN COMPONENTS

Use single-conductor, low capacity shielded wire for connecting preamplifier to amplifier. Keep leads under ten feet in length, un le s s emitter-follower output is employed.

Speakers may b e connected with standard flexible l i ne cord (zip-cord) and up to 100 feet of cab le may be used without appreciable loss.

Make certain that all audio cab le s are kept away from speaker cables, power cables, and power trans-formers; and that speaker cab le s are kept away from power cables.

POWER

Connect the l ine cord to a wall outlet supplying

117 volt AC, 50/60 cyc le power. Power to the ampli-fier may b e controlled by means of the Power ON-OFF switch located on the front panel. To have amplifier turned on and off by preamplifier, refer to Operation Section.

An AC receptacle h a s been included on the top of t he amplifier c h a s s i s to supply power to other components in a system, not exceeding 400 watts.

T h e receptacle is connected to the Power switch, and any component connected to i t will be turned off by the Power switch.

INPUT CONNECTIONS

High Impedance: The amplifier can be driven to full output, using the high impedance input, from any puts at 500/600 ohms balanced or unbalanced, con-nec t a Bogen TL600 plug-in transformer to the XI socket located on top of t h e chass i s . Connect the 500/600 ohm input to the L O Z terminals on t h e rear of t he amplifier. T h e connection may be grounded or left floating depending on the particular installation.

Bridging Inputs: The amplifier will accept bridg-ing inputs a t 10,000 ohms, by utilizing the Bogen TLlOK transformer. T h e TLlOK is plugged into the XI re-ceptacle, and the bridging input is connected to the L O 2 input on t h e rear of the amplifier.

Obtain ing s ignal from output of other power amplif ier: For amplifiers with' a 70 volt output tap , the following circuit is recommended to deliver t he signal required to drive the HI Z input receptacle of the MBT60 booster amplifier.

I

OUTPUT

TERMINAL

STRIP OF

DRIVER

AMPLIFIER

w TO HIGH

IMPEDANCE

INPUT OF

POWER

AMPLIFIER

I 74-1162-A

AT 7 0 V RI = 47K .1/2W

AT 25V R I = IOK .1/2W

NOTE: The network above is in addition to the normal load (loudspeakers, etc.) on the output of the driver amplifier.

OUTPUT CONNECTIONS

T h e MBT60 booster amplifier may be connected to speakers rated at 8 or 16 ohms or used with 25 volt or 70 volt constant voltage line systems.

For 8 or 16 ohm operation, connect one lead from the speakers to the COM 1 terminal and the other to the appropriate 8 or 16 ohm terminal on the rear of the amplifier chass i s . For 25 volt operation connect leads between 25 v (10.4 ohm) and COM 1; for balanced 25 volt operation disconnect shorting link between COM 1 and GND. For 70 volt unbalanced operation connect l eads t o 70 V (82 ohm) terminals and COM 2 terminal and connect shorting wire from COM 2 terminal to GND if grounding is desired. For 70 volt balanced operation connect l eads to 70 V (82 ohm) terminal and COM 2 terminal; do not connect shorting wire from COM 2 to GND.

REMOTE STANDBY AND VOLUME CONTROL

The MBT60 amplifier may be remotely controlled for standby operation by utilizing the LVP-1 accessory.

P l u g th i s accessory into the REMOTE STANDBY & VOLUME socket on the top panel of the amplifier chass i s , Mount a SPST switch, which is not supplied with the amplifier, a t a convenient remote position.

Connect one s ide of the switch to the REMOTE terminal and the other s ide to the GND terminal of the output strip of the amplifier.

For remote volume control, the Bogen RVC-1 accessory i s used in conjunction with the LVP-1.

P lug the LVP-1 accessory into the REMOTE STAND- BY & VOLUME socket. Connect the RVC-1 remote volume control between the REMOTE and GND terminals on the output strip.

- 3 -

The length of control cab le which can b e used between the remote switch or remote control and the amplifier i s limited by the DC resistance of the con-trol leads. The total length of control cab le used, therefore, should not exceed the following:

#22 AWG wire - 3000 feet

#18 AWG wire - 8000 feet

Two wire parallel or twisted unshielded

GROUNDING THE UNIT

Ground t h e amplifier by attaching a wire from a

GND terminal on the c h a s s i s rear to a good ground such a s the metal frame of the wall outlet or a water or steam pipe. FIGURE 1 - MBT60 REAR PANEL

OPERATION

Although the POWER switch on the front panel may be ’used to turn the booster amplifier on and off, i t is advantageous to control the unit from the pre-amplifier. For th i s reason, the AC power cord of the MBT60 should be connected to the controlled auxiliary power receptacle of the preamplifier. A pilot light on the front panel indicates that power h a s been applied to the amplifier.

The volume control on the rear c h a s s i s is used primarily t o compensate for variations in preamplifier output levels. Thus, i f t he preamplifier output i s very high, t he user will’find that i t is necessary to operate the preamplifier’s volume control near minimum to prevent “blasting” volume output from the speaker system. Conversely, if the preamplifier output is low, the preamplifier’s volume control may have to be operated near maximum to achieve sufficient volume.

T h e volume control on the MBT60 thus permits the user to preset t h e gain of the amplifier so that the preamplifier’s volume control is operated in i t s mid-range t o achieve the desired volume level range.

Th i s control, which need be s e t only once on instal-lation, is a screwdriver adjustment.

The SPEECH-MUSIC switch is located on the top of the amplifier. Set th i s switch to SPEECH position to provide optimum speech response.

SERVICE

BOGEN SERVICE

We are interested in your Bogen unit for as long as you have it. If trouble ever develops with your unit, p lease do not hes i ta te to ask our advice or assistance.

Information can be obtained by writing to: Service Department, Bogen Communications, P.O. Box 500, Paramus, New Jersey 07652.

When communicating with u s give the model number of your unit. Completely describe the difficulty en-countered. Describe t h e effects each operating control h a s upon the symptoms of trouble. Include de ta i l s on electrical connections to associated equipment and l i s t such equipment.

When we receive th i s information, we will send you service information if the trouble appears to be simple (e. g. bad component, incorrect connections).

If trouble requires servicing, we sha l l send you the name and address of t h e nearest Bogen authorized serv ice agency to which you can send your unit for repair.

When shipping your unit, pack instrument well, using the original shipping carton and filler material to prevent damage in transit. Send unit, fully insured and prepaid, v i a railway express. Do not ship via parcel post un less so instructed. The unit will b e promptly repaired and returned to you v ia express collect.

PILOT LIGHT REPLACEMENT

The pilot light is a long life bulb which will seldom require replacement. If i t should burn out, re-move the bottom ccver by removing the holding screws.

Replace with an identical No. 19 bulb. o

- 4 -

CIRCUIT B R E A K E R

The amplifier circuitry is protected against el-ectrical overload by a l# ampere circuit breaker. To rese t t h e breaker, p r e s s t h e red reset button, located

If t h e circuit breaker tr ips again, do not attempt to operate t h e unit. Check the amplifier t o determine the cause of the overload, or consult a Bogen r e p r e sen ta t ive or competent serviceman.

I on the rear c h a s s i s lef t side, as shown in figure 1.

TRANSISTOR REPLACEMENT

Trans is tors and semiconductor diodes do not

I ordinarily require routine testing. When the receiver does not perform properly and i t is suspected that a transistor or diode is a t fault, only a qualified technician should t e s t them.

However, if previous tests by a technician in-d ica te that a transistor might b e faulty, i t must b e removed from the circuit for checking. The plug-in transistors, of course, can be eas i ly replaced. To replace plug-in transistors u s e Dow Coming No. 340 Compond Silicon Grease (or equivalent). Brush com-pound on hea t sink and transistor; b e certain that no foreign matter is on hea t Sink or transistor. To insure proper contact, securely screw down plug-in transistors.

NOTE

When the MBT60 i s used in conjunction with a Bogen MXM-A Mixer Preamplifier t he following pre-cautions should b e observed.

Because of t h e high output and sensit ivity of the MXM-A which makes possible the paralleling of up to three (MXM-A) uni t s (with a total of 15 available microphone inputs), it is important that the overall system gain is properly adjusted (reduced) when only one MXM-A is used with MBT60 booster amplifier(s).

The MBT60 Volume control should b e adjusted to provide a high impedance booster input sensit ivity of 20 volts for full output; or a sensit ivity of approxi-mately 4 volts when the input t o the booster amplifier is 600 ohms (i.e. with TL600 line transformer). This is accomplished by rob t ing the MBT60 VOLUME control approximately f /4 turn clockwise from the off position.

With the MXM-A MASTER gain control s e t at “6”, all channels will have more than sufficient sensitivity.

When the MXM-A and MBT60 are both adjusted as described above unnecessary and excess ive overall system gain, hum noise or possible oscillation will be avoided.

REPLACEMENT PARTS

The components used in BOGEN equipment, with excepfion of items l i s ted below, are standard parts available through all reputable parts jobbers.