APCS SIR Sect J Att J.1.1 Amend 3.docx

Federal Aviation Administration

U.S. Department of Transportation Federal Aviation Administration VoICE APC System Technical Specification November 15, 2022

Focal Point Air Traffic Organization (ATO) - Technical Operations Air Traffic Control (ATC) Communications Services Voice Switching and Recording Team, AJM-315

Federal Aviation Administration 800 Independence Avenue SW Washington, DC 20591

TABLE OF CONTENTS

Contents

Figures

Tables

SECTION 1: INTRODUCTION

INTRODUCTION

Scope This specification contains the technical requirements of the Federal Aviation Administration (FAA) for the National Airspace System (NAS) Air-to-Ground Protocol Converter (APC) System. This specification cites Government and non-Government standards, orders, handbooks, and other pertinent documents to ensure the APC System will possess the necessary functional performance and interface requirements essential to the NAS.

NOTES:

1. The FAA is currently pursuing an IP only Transport approach for the APC communications links, which is represented in this specification with unshaded text, figures, and requirements. Any “grey” shaded text, figures, and requirements in this specification and the APC to Analog Radio Control Systems Interface Requirements Document (IRD) represents Analog Transport areas for APC communications links, which will be added later after In Service Decision (ISD) through a Preplanned Engineering Change.

2. Due to the delayed need for the Local Legacy Radio APC (LLR-APC) capability, the FAA intends to put development and testing of the LLR-APC functionality on hold until after ISD. Any “turquoise” shaded text, figures, and requirements in this specification and the APC to Analog Radio Control Systems Interface Requirements Document (IRD) represents LLR-APC areas, which will be added later after In Service Decision (ISD) through a Preplanned Engineering Change.

3. The FAA is requiring new ATC systems to support IPv6 and the IPv6 requirement for the APC System would be implemented after In Service Decision (ISD. Any “green” “shaded text, figures, and requirements in this specification and the APC System to Government Transport System (GTS) Interface Requirements Document (IRD) represents IPv6 areas, which will be added later after In Service Decision (ISD) through a Preplanned Engineering Change.

Document Overview Section 1 (this section) describes the scope of this specification, gives an overview of this specification, and gives an overview of the APC System. It is intended to be descriptive in nature and contains no binding requirements.

Section 2 lists the documents that are cited within subsequent sections as a part of binding requirements.

Section 3 lists system requirements, which includes references to Interface Requirements Documents (IRDs) where applicable.

Section 4 contains verification requirements.

Section 5 lists Acronyms and Abbreviations.

Section 6 provides a Glossary.

Section 7 provides the ED-137C Volume 1 Clarification Matrix System Overview Figure 11 shows a high-level, conceptual system diagram with the proposed new elements of the FAA’s planned Voice over IP Communication Enterprise (VoICE) shaded in light blue. This specification covers the Air-to-Ground Protocol Converter (APC) element, where the APC is utilized to replace the FAA’s legacy Radio Control Equipment (RCE) and also translate between the FAA’s legacy radio interfaces and VoIP (ED-137) Air-to-Ground (A/G) interfaces.

Figure 11 - Conceptual System Diagram of the FAA's VoICE

SECTION 2: APPLICABLE DOCUMENTS

APPLICABLE DOCUMENTS

The following documents form a part of this specification to the extent specified herein. In case of any discrepancy between these documents and specific requirements of this specification, this specification must be considered the superseding document unless otherwise directed by the government.

Copies of government documents may be obtained as directed by the contracting officer.

Copies of non-government documents are generally available in technical libraries or may be obtained from their originators.

When the requirements of this document and referenced applicable documents are in conflict, this document has precedence over all documents referenced herein.

If either two or more referenced applicable documents are in conflict or two or more sections of this document are in conflict, the APC System program office must be notified to resolve the conflict.

Government Documents Specifications FAA-G-2100H, Electronic Equipment, General Requirements (May 9, 2005).

Standards

1. DOT HF-STD-001B, Human Factors Design Standard (December 30, 2016).

FAA-STD-019f, Lightning and Surge Protection, Grounding, Bonding and Shielding Requirements for Facilities and Electronic Equipment (October 18, 2017).

MIL-STD-461G, Requirements for the Control of Electromagnetic Interference Characteristics of Subsystems and Equipment (December 11, 2015).

MIL-STD-1472G, Human Engineering (August 23, 1999).

Other FAA Documents

1. FAA Order 3900.19C, Occupational Safety and Health Program (March 11, 2019).

FAA Order 8040.4B, Safety Risk Management (May 2, 2017).

Attachment J.2.1, VoICE APC System to Analog Radio Control Systems IRD.

Attachment J.2.2, VoICE APC System to FAA Facility Power IRD.

Attachment J.2.3, VoICE APC System to Government Transport System (GTS) IRD.

Attachment J.1.13, VoICE APC System Human Factors Design Tailored Checklist.

Federal Regulations

1. Title 29 CFR Part 1910, Occupational, Safety and Health Standards.

Title 29 CFR Part 1926, Occupational Safety and Health Administration, Labor.

Title 47 CFR Part 15, Radio Frequency Devices.

Title 47 CFR Part 68, Federal Communications Commission Description of Standard Regulations Program Connection Configuration.

FPMR 101-42, Utilization and Disposal of Hazardous Materials and Certain Categories of Property.

Other Federal Documents

1. MIL-HDBK-454B, General Guidelines for Electronic Equipment (April 15, 2007).

Non-Government Documents

1. ANSI/IPC-T-50M, American National Standards Institute (ANSI) Terms and Definitions for Interconnecting and Packaging Electronic Circuits (May 2015).

EUROCAE Document ED-137C Volume 1, Interoperability Standards for VoIP ATM Components (April 2017).

IEC 61000-4-2 ed2.0 b:2008, Electromagnetic Compatibility (EMC) – Part 4-2 Testing and Measurement Techniques – Electrostatic Discharge Immunity International Electromechanical Commission (December 9, 2008).

IPC-2221B, Generic Standard on Printed Board Design (November 2012).

ITU-T Recommendation P.862, Perceptual Evaluation of Speech Quality (PESQ): An objective method for end-to-end speech quality assessment of narrow-band telephone networks and speech codecs (February 2001).

ITU-T Recommendation P.862.1, Mapping function for transforming P.862 raw result scores to MOS-LQO (November 2003).

NFPA 70, National Electrical Code (NEC), National Fire Protection Association (2020).

NFPA 70E, Standard for Electrical safety in the workplace (2018).

GR-63-CORE, NEBS Requirements: Physical Protection, Issue 5 (December 2017).

IEC 60950-1, Information Technology Equipment - Safety - Part 1: General Requirements, 2.2 Edition, May 2013.

ITU-T Recommendation G.711 – Pulse Code Modulation (PCM) of Voice Frequencies, November 1988.

ITU-T Recommendation G.729 – Coding of speech at 8Kbit/s using conjugate structure algebraic-code-excited linear-prediction (CS-ACELP), Annex A: Reduced complexity 8Kbit/s CS-ACELP speech codec, June 2012.

SECTION 3: REQUIREMENTS

REQUIREMENTS

The Air-to-Ground Protocol Converter (APC) System is comprised of two (2) fundamental elements, the Air-to-Ground Protocol Converter (APC) and the Air-to-Ground Protocol Converter Management Subsystem (APCMS), which are highlighted in light blue in Figure 31. As defined in this specification, a single APC System can contain multiple APCs.

As shown in Figure 31, the APCMS contains the Local Manager and the APC Network components for the APC System.

To translate the protocol between the FAA’s Legacy and VoIP resources for Air-to-Ground communications, the APC System can support interfaces for Legacy Voice Communication Systems (VCSs), Legacy Radio Resources, Voice over IP (VoIP) VCSs, and VoIP Radios.

Figure 31 - Functional Diagram of the APC System As shown in Figure 32, the APC supports three configurations. The APC is utilized in the following configurations:

Local Legacy Radio-Air-to-Ground Protocol Converter (LLR-APC):

a. Provides VoIP VCSs with analog access to Legacy Local Radios (single frequency)

b. Provides Legacy Voice Switch Bypass (VSBP) with VoIP access to IP Radios (single frequency) Local-Air-to-Ground Protocol Converter (L-APC):

a. Replaces the Control-Radio Control Equipment (C-RCE) and provides analog interface with the Remote-Air-to-Ground Protocol Converter (R-APC)

1. Provides Legacy VCS with access to analog port of R-APC via analog voice and signaling interface of L-APC

2. Provides VoIP VCS with access to analog port of R-APC via VoIP port of L-APC

b. Provides Legacy VCS with access to VoIP port of R-APC via VoIP port of L-APC (see Figure 32) Remote-Air-to-Ground Protocol Converter (R-APC):

a. Replaces the Remote-Radio Control Equipment (R-RCE) and provides analog interface with the L-APC to provide remote access to up to eight Legacy Radios

b. Provides VoIP VCS and/or L-APC (VoIP port) with VoIP (ED-137) access to up to eight Legacy Radios or eight IP Radios NOTE: For VoIP VCS and/or L-APC (VoIP port) with VoIP (ED-137) access, the R-APC can control either up to eight Legacy Radios or up to eight IP Radios, but the R-APC will not control a mix of both Legacy and IP radios.

The APC requirements in this specification are written utilizing designators of “LLR-APC”, “L-APC”, and “R-APC” to directly correlate the functional requirements with the associated configurations of the APC. Any requirement written as just “APC” would apply to all configurations of the APC. In addition, any system requirements will be written as “APC System” and will apply to all elements defined in Figure 31. Note that an APC System can encompass APCs of different configurations (LLR-APCs, L-APCs, and R-APCs). The APCs within a single APC System can be located at multiple facilities, due to APCs at radio facilities (R-APCs) being part of a VCS facility’s managed resources. The APCMS for an APC System will always reside at a VCS facility.

NOTE: Requirement references to “TX” apply to the transmitter and requirement references to “RX” correspond to the receiver. For example, TX audio is audio going to the transmitter and RX audio is coming from the receiver.

Figure 32 - Functional Configurations of the APC

Functional Requirements NOTE: For all requirement references in this specification to ED-137C, refer to the ED-137C Volume 1 Clarification Matrix in Section 7 of this specification for the specific applicability of each ED-137 requirement.

1. The APC System must support implementation of Analog Transport Preplanned Engineering Change, as defined in section 1.1, without any impact to ongoing ATC operations on the APC System.

1. The APC System must support implementation of LLR-APC Preplanned Engineering Change, as defined in section 1.1, without any impact to ongoing ATC operations on the APC System.

1. The APC System must support implementation of IPv6 Preplanned Engineering Change, as defined in section 1.1, without any impact to ongoing ATC operations on the APC System.

LLR-APC Functions The LLR-APC will be utilized for two applications (see Figure 32). The first application will be to provide a VoIP VCS with access to Local Legacy Radios and the second application will be to provide the existing, analog Voice Switch Bypass (VSBP) found in Terminal Facilities with access to IP Radios. The VSBP provides Air Traffic Controllers emergency access to air-to-ground (A/G) radio transmitter and receivers during a failure of the VCS.

VoIP VCS Application (Local Legacy Radios) This section covers the LLR-APC requirements for providing VoIP VCS connections to legacy local radios, which are defined as analog radios for a single frequency.

1. The LLR-APC must translate between ED-137 VoIP interface and analog interface (voice and signaling) of legacy local radios.

1. The LLR-APC must meet the requirements for interfacing with legacy local radios in accordance with section 3.2.1 of the APC to Analog Radio Control Systems Interface Requirements Document (IRD).

1. The LLR-APC must meet the requirements for interfacing with VoIP VCSs in accordance with ED-137C, Volume 1 per Clarification Matrix in Section 7 of this specification.

1. The LLR-APC must provide controls to limit the concurrent VoIP VCS SIP sessions allowed at the Network interface from one to a minimum of twelve.

1. The LLR-APC must provide access controls to designate which VoIP VCSs can establish SIP sessions with the LLR-APC.

LLR-APC Radio Control Signals (Local Legacy Radios) This section covers the LLR-APC radio control signals resulting from VoIP VCS ED-137 messages.

Push-to-Talk (PTT)

1. The LLR-APC must provide, upon reception of ED-137 message for PTT Main TX, a PTT signal to local main transmitter.

1. The LLR-APC must internally generate ED-137 message for PTT confirmation for local main transmitter.

The LLR-APC must provide, upon reception of ED-137 message for PTT Standby TX, a PTT signal to local standby transmitter.

The LLR-APC must internally generate ED-137 message for PTT confirmation for local standby transmitter.

The LLR-APC must provide, upon reception of ED-137 message for PTT Release Main TX, a PTT Release signal to local main transmitter.

The LLR-APC must internally generate ED-137 message for PTT Release confirmation for local main transmitter.

The LLR-APC must provide, upon reception of ED-137 message for PTT Release Standby TX, a PTT Release signal to local standby transmitter.

The LLR-APC must internally generate ED-137 message for PTT Release confirmation for local standby transmitter.

Main / Standby Selection

1. The LLR-APC must, upon reception of ED-137 message for main transmitter selection, provide voice and signaling for local main transmitter selection.

1. The LLR-APC must internally generate local main transmitter confirmation message (ED-137).

The LLR-APC must, upon reception of ED-137 message for standby transmitter selection, provide voice and signaling for local standby transmitter selection.

The LLR-APC must internally generate local standby transmitter confirmation message (ED-137).

The LLR-APC must, upon reception of ED-137 message for main receiver selection, provide voice and signaling for local main receiver selection.

The LLR-APC must internally generate local main receiver confirmation message (ED-137).

The LLR-APC must, upon reception of ED-137 message for standby receiver selection, provide voice and signaling for local standby receiver selection.

The LLR-APC must internally generate local standby receiver confirmation message (ED-137).

Squelch Break (SQB)

1. The LLR-APC must, when available, accept SQB signal from local main receiver and provide ED-137 message for Main RX SQB.

The LLR-APC must, when available, accept SQB signal from local standby receiver and provide ED-137 message for Standby RX SQB.

The LLR-APC must provide the option to internally generate SQB signals from selected receiver.

The LLR-APC must utilize VOX circuits described in section 3.2.1.10 to internally generate SQB signaling.

LLR-APC Radio Control Access to Local Legacy Radios This section covers the requirements of the LLR-APC granting radio control access between VoIP VCS control sites. Access connections for the LLR-APC are further illustrated in Figure 32.

1. The LLR-APC must accept radio control from up to 6 VoIP VCS control sites.

The LLR-APC must provide radio control PTT preemption of the lower and equal priority control sites for up to six VoIP VCSs.

The LLR-APC must, in the event of a loss of communications with one or more control sites, maintain communications with remaining operational control sites.

Non-Priority Mode This section covers the requirements of the LLR-APC for granting radio control access without PTT priority levels being assigned (i.e., all PTT priority levels equal).

1. The LLR-APC must, when control facilities have equal priority, provide a transmit voice path and PTT confirmation to that facility from which the PTT arrives first.

The LLR-APC must, when control facilities have equal priority, only allow one facility at a time to have control of the radios; subsequently, lockout the remaining control facilities, i.e., block the voice transmit path, PTT/PTT release, and M/S transmitter/receiver select capabilities of the remaining control facilities.

The LLR-APC must, when in “non-priority mode”, provide receive voice path continuously to all the control facilities.

The LLR-APC must, when in “non-priority mode” and upon release of PTT by the control facility that issued the PTT in progress, transmit a PTT release confirmation message to that control facility and terminate the lockout condition for the other control facilities.

The LLR-APC must, when in “non-priority mode” and upon release of PTT by the control facility that issued the PTT in progress, permit any previously blocked control facility, attempting to PTT, to acquire transmitter(s) without requiring the facility to release and reactivate PTT.

Prioritized Mode This section covers the requirements of the LLR-APC for granting radio control access with PTT priority levels being assigned.

1. The LLR-APC must arbitrate radio access permissions to all the connected control facilities based on their PTT priority levels.

The LLR-APC must, in an ED-137 multi-level PTT priority scheme (i.e., Test, Normal, Priority, and Emergency), permit the higher PTT priority facility to override the lower PTT priority control facility with respect to communicating on the frequency to which those control facilities have access.

The LLR-APC must provide a transmit voice path and PTT confirmation to the controlling facility when a controller at that facility asserts PTT.

The LLR-APC must, when PTT is active at a lower priority facility and a PTT signal is received from a higher priority facility, release the lower priority facility’s PTT control and lockout that facility while PTT is active from the higher priority facility.

The LLR-APC must, when in “prioritized mode”, provide receive voice path continuously to all the control facilities.

The LLR-APC must, when in “prioritized mode” and upon release of PTT by the control facility that issued the PTT in progress, transmit a PTT release confirmation message to that control facility and terminate the lockout condition for the other control facilities.

The LLR-APC must, when in “prioritized mode” and upon release of PTT by the control facility that issued the PTT in progress, permit any previously blocked control facility, attempting to PTT, to acquire transmitter(s) without requiring the facility to release and reactivate PTT.

Legacy VSBP Application (Local IP Radios) This section covers the LLR-APC requirements for providing the VSBP with connections to VoIP Radios.

1. The LLR-APC must translate between VSBP analog interface (voice and signaling) and ED-137 VoIP interface of IP local radios.

1. The LLR-APC must meet the requirements for interfacing with VSBP in accordance with section 3.2.2 of the APC to Analog Radio Control Systems Interface Requirements Document (IRD).

1. The LLR-APC must meet the requirements for interfacing with VoIP radios in accordance with ED-137C, Volume 1 per Clarification Matrix in Section 7 of this specification.

LLR-APC Radio Control Signals (Local IP Radios) This section covers the LLR-APC radio control messages resulting from VSBP signaling.

Push-to-Talk (PTT)

1. The LLR-APC must translate PTT signal received from the VSBP and provide associated PTT Main TX messages (ED-137) to the LLR-APC VoIP Interface.

1. The LLR-APC must translate PTT Release signal received from the VSBP and provide associated PTT Release Main TX messages (ED-137) to the LLR-APC VoIP Interface Main Radio Selection

1. The LLR-APC must translate Main transmitter select signal received from the VSBP and provide the associated Main transmitter selection messages (ED-137) to the LLR-APC VoIP Interface.

aa. The LLR-APC must translate Main receiver select signal received from the VSBP and provide the associated Main receiver selection messages (ED-137) to the LLR-APC VoIP Interface.

L-APC Functions This section covers the L-APC requirements for providing Legacy VCS and VoIP VCSs with access to R-APC via the analog protocol. The L-APC also provides Legacy VCS with access to VoIP port of R-APC.

1. The L-APC must translate between analog interfaces (voice and signaling) of Legacy VCS and analog protocol to R-APC.

The L-APC must translate between VoIP VCS interface (ED-137) and analog protocol to R-APC.

The L-APC must translate between analog interfaces (voice and signaling) of Legacy VCS and VoIP interface (ED-137).

The L-APC must meet the requirements for interfacing with the Legacy VCSs in accordance with sections 3.2.3, 3.2.4, 3.2.5, 3.2.6 and 3.2.7 of the APC to Analog Radio Control Systems IRD.

The L-APC must meet the requirements for interfacing with VoIP VCSs in accordance with ED-137C, Volume 1 per Clarification Matrix in Section 7 of this specification.

The L-APC must meet the requirements for interfacing with R-APC VoIP port in accordance with ED-137C, Volume 1 per Clarification Matrix in Section 7 of this specification.

The L-APC must provide controls to limit the concurrent VoIP VCS SIP sessions allowed at the L-APC network interface from one to a minimum of twelve.

The L-APC must provide access controls to designate which VoIP VCSs can establish SIP sessions with the L-APC.

The L-APC must, for separate Main/Standby radio interfaces to a local legacy VCS (Terminal ATC Facilities), preclude switching the M/S radio interfaces to match the R-APC radio selection of M/S radios when another control site (L-APC or VoIP VCS) causes the selection to change at the R-APC.

The L-APC must, when it supports Back-Up Emergency Communications (BUEC), utilize ED-137 protocol to notify connected VoIP VCSs whenever the L-APC BUEC resource is selected.

The L-APC must provide an option to block F2 audio if both F1 and F2 PTT are active. NOTE: This feature will prevent unwanted uplink audio distortion if F1 and F2 uplink audio are the same and are fed by two separate interfaces from a Legacy VCS.

L-APC Analog Protocol Functions This section covers the requirements of the L-APC analog protocol functions for interfacing with R-APC. Requirements for the R-APC analog protocol functions are covered in section 3.1.3.1. NOTE: In lieu of a Vendor-Specific analog protocol with the R-APC, the Vendor solution can be based on the FAA’s existing RCE protocol.

1. The L-APC must support an analog protocol for interfacing with the R-APC.

The L-APC must provide an interface (channel) to the R-APC that supports the capability to transmit and receive voice and radio control signals for up to two A/G frequencies over a single four-wire voice grade transmission path.

The L-APC must permit control over any of the two analog channel frequencies one at a time.

The L-APC must permit control of the two analog channel frequencies simultaneously.

The L-APC must provide monitoring, maintenance, and configuration of the R-APC over the same single four-wire voice grade interface used for voice and radio control signals.

The L-APC must permit communication on both frequencies (F1 and F2) simultaneously with audio summing for each analog channel.

The L-APC must meet the requirements for interfacing with the R-APC in accordance with section 3.2.2 of the APC to Analog Radio Control Systems IRD.

The L-APC must provide three pass-through RS-232 ports per section 3.2.2.2 of the APC to Analog Radio Control Systems IRD to support the transport of remote monitoring and control data. NOTE: The remote monitoring and control data is external of the APC System and the RS-232 pass-through function is only provided when Analog Protocol is utilized between the L-APC and R-APC.

L-APC Analog Protocol Operational Configurations The L-APC will provide three operational configurations to support analog protocol control modes of the R-APC. The L-APC will support the following operational configurations: Separated TX and RX Configuration, Primary and Backup Configuration, and Dual Control Configuration as shown in Figure 33.

1. The L-APC must, as shown in Figure 33, support the APC “Separated TX and RX Configuration” (analog protocol) in which the L-APC communicates with two separate R-APCs.

The L-APC must, as shown in Figure 33, support the APC option for switched backup trunks for each of the two active trunks to the two R-APCs utilized in the “Separated TX and RX Configuration” (analog protocol).

The L-APC must, as shown in Figure 33, support the APC “Primary and Backup Configuration” (analog protocol) in which the L-APC utilizes a Primary and Backup trunk to communicate with a single R-APC.

The L-APC must support the APC option to automatically or manually switch between primary and hot backup trunk communications to the R-APC in the “Primary and Backup Configuration” (analog protocol).

The L-APC must, for the “Primary and Backup Configuration” (analog protocol), maintain a hot backup trunk with audio only being placed on the active trunk.

The L-APC must support the APC option to disable the backup trunk interface in the APC “Primary and Backup Configuration” (analog protocol).

The L-APC must, as shown in Figure 33, support the APC “Dual Control Configuration” (analog protocol) in which two separate control sites (L-APCs) communicate with the same R-APC.

The L-APC must, as shown in Figure 33, support the APC option for a switched backup trunk for the active trunk to the R-APC utilized in the “Dual Control Configuration” (analog protocol).

The L-APC must, as shown in Figure 33, be configurable to support two active and two back-up four-wire trunk interfaces to the R-APC for analog protocol operational configurations.

The L-APC must preclude automatically switching to a failed trunk in a “Primary / Backup Configuration” (analog protocol).

The L-APC must preclude automatically switching to a looped trunk in a “Primary and Backup Configuration” (analog protocol).

The L-APC must, in the APC "Primary and Backup Configuration"(analog protocol), prevent TX and RX Main/Standby selection on the frequency of any actively keyed transmitters.

The L-APC must, in the APC “Separated TX and RX Configuration” (analog protocol), prevent TX and RX Main/Standby selection on the frequency of any actively keyed transmitters.

Figure 33 - L-APC Analog Protocol Operational Configurations L-APC Recovery from Analog Communications Path Failure

1. The L-APC must detect communication path failures on primary and backup analog communication paths to the R-APC (if a backup path is available).

The L-APC must, in the event of analog communication path failures to the R-APC, automatically re-establish communications over an alternate analog communications path when available, in less than or equal to six seconds.

The L-APC must provide the option to manually switch between analog communication paths to the R-APC.

The L-APC must adopt the operator-selected state in effect prior to analog communication path failure to the R-APC, in less than or equal to three seconds, following the re-establishment of communications without operator intervention.

The L-APC must, in the case of analog communication path interruption with the R-APC exceeding three seconds, release all confirmation signals.

The L-APC must, if no alternate analog communication path has been configured to the R-APC, prohibit either automatic or manual switching to a non-existing transmission path.

The L-APC must, in the event of analog communication path failure to the R-APC adopt a timer of less than 6 seconds before attempting to switch to another path, if after the first attempt the L-APC fails to “lock” to the R- APC. NOTE: The L-APC timer will need to be configured as necessary (different than R-APC) to ensure the ability to enter a locked state.

The L-APC must, in the event of analog communication path failures to the R-APC, automatically re-establish communications over the same communications path upon availability, in less than or equal to 6 seconds, when no alternate communications path is provided.

The L-APC must, for an analog transmission path interruption with the R-APC exceeding three seconds, provide an option to terminate all SIP sessions between the L-APC and all VoIP VCSs, until the APC analog transmission path is restored.

L-APC Analog Protocol Encoding and Decoding of Radio Control and Voice Signals

1. The L-APC must encode and decode data messages to and from the R-APC over a single four-wire voice grade transmission path.

The L-APC must verify all analog protocol control messages to the R-APC with transmitted error check sequence bits to ensure command integrity.

The L-APC must combine voice and data for simultaneous transmission to the R-APC over a single four-wire voice grade transmission path.

The L-APC must transmit and receive analog protocol data messages to and from the R-APC using modem (modulator/demodulator) operating in the 2500 to 3000 Hz frequency band. NOTE: This is what the legacy RCE currently supports and it may not be the final requirement for the APC.

The L-APC must low pass filter voice signals and transmit them to the R-APC in the 300 to 2500 Hz frequency band. NOTE: This is what the legacy RCE currently supports and it may not be the final requirement for the APC.

L-APC Radio Control Functions (Analog Protocol)

1. The L-APC must, per section 3.1.2.1.4.1, encode analog protocol for the Legacy VCS radio control signals defined in section 3.2.4 (Voltage Interface) of the APC to Analog Radio Control Systems IRD for up to two A/G frequencies associated with an APC channel and then transmit them to the R-APC.

The L-APC must, per section 3.1.2.1.4.1, decode analog protocol for the radio confirmation signals received from the R-APC for up to two A/G frequencies associated with an APC channel and provide them to the Legacy VCS as confirmation signals defined in section 3.2.4 (Voltage Interface) of the APC to Analog Radio Control Systems IRD.

The L-APC must, per section 3.1.2.1.4.1, encode analog protocol for the Legacy VCS radio control signals defined in section 3.2.5 (Contact Closure Interface) of the APC to Analog Radio Control Systems IRD for up to two A/G frequencies associated with an APC channel and then transmit them to the R-APC.

The L-APC must, per section 3.1.2.1.4.1, decode analog protocol for the radio confirmation signals received from the R-APC for up to two A/G frequencies associated with an APC channel and provide them to the Legacy VCS as confirmation signals defined in section 3.2.5 (Contact Closure Interface) of the APC to Analog Radio Control Systems IRD.

The L-APC must, per section 3.1.2.1.4.1, encode analog protocol for the Legacy VCS PTT/PTT Release signal as defined in section 3.2.6 (BUEC Interface) of the APC to Analog Radio Control Systems IRD for A/G frequency associated with an APC channel and then transmit it to the R-APC. NOTE: All other BUEC signals defined in section 3.2.6 of the APC to Analog Radio Control Systems IRD are only utilized at the Legacy VCS/ L-APC interface.

The L-APC must, per section 3.1.2.1.4.1, encode analog protocol for the VoIP VCS radio control messages defined in ED-137C, Volume 1 for up to two A/G frequencies associated with an APC channel and then transmit them to the R-APC.

The L-APC must, per section 3.1.2.1.4.1, decode analog protocol for the confirmation signals received from the R-APC for up to two frequencies associated with an APC channel and provide them to the VoIP VCS as radio confirmation messages defined in ED-137C, Volume 1.

L-APC Control Signals The following requirements are for the L-APC to encode radio control commands and decode radio control confirmations for both Legacy and VoIP VCSs per requirements in section 3.1.2.1. 4. Section 3.1.2.3 covers the requirements for the L-APC granting radio control access between a single Legacy VCS control site and multiple (up to six) VoIP VCS control sites, to a single R-APC Resource.

Push-to Talk (PTT)

1. The L-APC must apply analog protocol encoding for up to two independent PTT signals (F1 and F2) received from the Legacy VCS and transmit them over the four-wire voice grade transmission path to the R-APC.

The L-APC must apply analog protocol encoding for up to two independent PTTs received from the VoIP VCS message (ED-137) and transmit them over the four-wire voice grade transmission path to the R-APC.

The L-APC must decode analog protocol for up to two independent PTT confirmation signals received from the R-APC over the four-wire voice grade transmission path and provide associated PTT confirmation signals to the Legacy VCS.

The L-APC must decode analog protocol for up to two independent PTT confirmation signals received from the R-APC over the four-wire voice grade transmission path and provide associated PTT confirmations in a message (ED-137) to the VoIP VCS.

The L-APC must apply analog protocol encoding for up to two independent PTT Release signals received from the Legacy VCS and transmit them over the four-wire voice grade transmission path to the R-APC.

The L-APC must apply analog protocol encoding for up to two independent PTT Releases received from the VoIP VCS message (ED-137) and transmit them over the four-wire voice grade transmission path to the R-APC.

The L-APC must decode analog protocol for up to two independent PTT Release confirmation signals received from the R-APC over the four-wire voice grade transmission path and provide associated PTT Release confirmation signals to the Legacy VCS.

The L-APC must decode analog protocol for up to two independent PTT Release confirmation signals received from the R-APC over the four-wire voice grade transmission path and provide associated PTT Release confirmations in a message (ED-137) to the VoIP VCS.

Main / Standby Radio Selection

1. The L-APC must apply analog protocol encoding for up to two independent M/S transmitter select signals received from the Legacy VCS and transmit them over the four-wire voice grade transmission path to the R-APC.

The L-APC must apply analog protocol encoding for up to two independent M/S transmitter select commands received from the VoIP VCS message (ED-137) and transmit them over the four-wire voice grade transmission path to the R-APC.

The L-APC must decode analog protocol for up to two independent M/S transmitter select confirmation signals received from the R-APC over the four-wire voice grade transmission path and provide associated M/S transmitter select confirmations to both the Legacy VCS and up to six VoIP VCSs.

The L-APC must apply analog protocol encoding for up to two independent M/S receiver select signals received from the Legacy VCS and transmit them over the four-wire voice grade transmission path to the R-APC.

The L-APC must apply analog protocol encoding for up to two independent M/S receiver select commands received from the VoIP VCS message (ED-137) and transmit them over the four-wire voice grade transmission path to the R-APC.

The L-APC must decode analog protocol for up to two independent M/S receiver select confirmation signals received from the R-APC over the four-wire voice grade transmission path and provide associated M/S receiver select confirmations to both the Legacy VCS and up to six VoIP VCSs.

Remote Receiver Mute

1. The L-APC must apply analog protocol encoding for up to two independent receiver mute signals received from the Legacy VCS and transmit them over the four-wire voice grade transmission path to the R-APC.

The L-APC must apply analog protocol encoding for up to two independent receiver mute commands received from the VoIP VCS message (ED-137) and transmit them over the four-wire voice grade transmission path to the R-APC.

The L-APC must decode analog protocol for up to two independent receiver mute confirmation signals received from the R-APC over the four-wire voice grade transmission path and provide associated receiver mute confirmations to the Legacy VCS and up to six VoIP VCSs.

The L-APC must apply analog protocol encoding for up to two independent receiver unmute signals received from the Legacy VCS and then transmit them over the four-wire voice grade transmission path to the R-APC.

The L-APC must apply analog protocol encoding for up to two independent receiver unmute commands received from the VoIP VCS message (ED-137) and transmit them over the four-wire voice grade transmission path to the R-APC.

The L-APC must decode analog protocol for up to two independent receiver unmute confirmation signals received from the R-APC over the four-wire voice grade transmission path and provide associated receiver unmute confirmations to both the Legacy VCS and up to six VoIP VCSs.

The L-APC must provide the option for muting the APC analog channel receive path during active PTT.

Squelch Break (SQB)

1. The L-APC must decode analog protocol for up to two independent SQB signals received from the R-APC over the four-wire voice grade transmission path and provide associated SQB indications to both the Legacy VCS and up to six VoIP VCSs.

The L-APC must provide the option to internally generate SQB signal and provide associated SQB indications in a message (ED-137) to the VoIP VCS. NOTE: This option allows for the L-APC to locally generate SQB signal, versus waiting for delayed, independent SQB signals from R-APC via the analog protocol. The delay in receiving SQB signals from R-APC, via the analog protocol, may result in voice clipping, due to ED-137 not passing audio to VoIP VCS until arrival of SQB signal from R-APC.

The L-APC must utilize VOX circuits described in section 3.2.1.10 to internally generate SQB signaling.

Automatic Gain Control (AGC)

1. The L-APC must decode analog protocol for up to two independent AGC signals received from the R-APC over the four-wire voice grade transmission path and provide associated AGC values in a Signal Quality Information (SQI) message (ED-137) to the VoIP VCS. NOTE: Legacy VCS does not utilize AGC voltage, but VoIP VCS could use it for Best Signal Selection (BSS).

L-APC VoIP Functions for Legacy VCS This section covers requirements for the L-APC to provide Legacy VCS with VoIP access to R-APC.

1. The L-APC must support a separated TX and RX configuration (IP Transport) in which the L-APC communicates with two separate R-APCs, where one R-APC supports transmitters, and another R-APC supports receivers.

L-APC Radio Control Functions (VoIP)

1. The L-APC must, per section 3.1.2.2.1.1, translate the Legacy VCS radio control signals defined in section 3.2.4 (Voltage Interface) of the APC to Analog Radio Control Systems IRD and provide associated command in a message (ED-137) to the L-APC VoIP Interface.

The L-APC must, per section 3.1.2.2.1.1, translate the radio confirmation messages (ED-137) received from the L-APC VoIP Interface and provide them to the Legacy VCS as confirmation signals defined in section 3.2.4 (Voltage Interface) of the APC to Analog Radio Control Systems IRD.

The L-APC must, per section 3.1.2.2.1.1, translate the Legacy VCS radio control signals defined in section 3.2.5 (Contact Closure Interface) of the APC to Analog Radio Control Systems IRD and provide associated command in a message (ED-137) to the L-APC VoIP Interface.

The L-APC must, per section 3.1.2.2.1.1, translate the radio confirmation messages (ED-137) received from the L-APC VoIP Interface and provide them to the Legacy VCS as confirmation signals defined in section 3.2.5 (Contact Closure Interface) of the APC to Analog Radio Control Systems IRD.

The L-APC must, per section 3.1.2.2.1.1.1, translate the Legacy VCS PTT/PTT Release signal defined in section 3.2.6 (BUEC Interface) of the APC to Analog Radio Control Systems IRD and provide associated command in a message (ED-137) to the L-APC VoIP Interface. NOTE: All other BUEC signals defined in section 3.2.6 of the APC to Analog Radio Control Systems IRD are only utilized at the Legacy VCS/ L-APC interface.

L-APC Control Signals Push-to-Talk (PTT)

1. The L-APC must translate up to two independent PTT signals (F1 and F2) received from the Legacy VCS and provide associated PTTs in a message (ED-137) to the L-APC VoIP Interface.

The L-APC must translate up to two independent PTT confirmations in a message (ED-137) received from the L-APC VoIP Interface and provide associated PTT confirmation signals to the Legacy VCS.

The L-APC must translate up to two independent PTT Release signals (F1 and F2) received from the Legacy VCS and provide associated PTT Releases in a message (ED-137) to the L-APC VoIP Interface.

The L-APC must translate up to two independent PTT Release confirmations in a message (ED-137) received from the L-APC VoIP Interface and provide associated PTT Release confirmation signals to the Legacy VCS.

Main / Standby Radio Selection

1. The L-APC must translate up to two independent M/S transmitter select signals received from the Legacy VCS and provide the associated M/S transmitter selection in a message (ED-137) to the L-APC VoIP Interface.

The L-APC must translate up to two independent M/S transmitter confirmations in a message (ED-137) received from the L-APC VoIP Interface and provide associated M/S transmitter confirmation signals to the Legacy VCS.

The L-APC must translate up to two independent M/S receiver select signals received from the Legacy VCS and provide the associated M/S receiver selection in a message (ED-137) to the L-APC VoIP Interface.

The L-APC must translate up to two independent M/S receiver confirmations in a message (ED-137) received from the L-APC VoIP Interface and provide associated M/S receiver confirmation signals to the Legacy VCS.

Remote Receiver Mute

1. The L-APC must translate up to two independent receiver mute signals received from the Legacy VCS and provide the associated receiver mute selection in a message (ED-137) to the L-APC VoIP Interface.

The L-APC must translate up to two independent receiver mute confirmations in a message (ED-137) received from the L-APC VoIP Interface and provide associated receiver mute confirmation signals to the Legacy VCS.

The L-APC must translate up to two independent receiver unmute signals received from the Legacy VCS and provide the associated receiver unmute selection in a message (ED-137) to the L-APC VoIP Interface.

The L-APC must translate up to two independent receiver unmute confirmations in a message (ED-137) received from the L-APC VoIP Interface and provide associated receiver unmute confirmation signals to the Legacy VCS.

The L-APC must provide the option for muting the APC receive audio path during active PTT.

Squelch Break

1. The L-APC must translate up to two independent SQBs in a message (ED-137) received from the L-APC VoIP Interface and provide associated SQB signals to the Legacy VCS.

L-APC Radio Control Access to R-APC (Analog Port) Between Legacy VCS and VoIP VCS Users This section covers requirements for the L-APC granting radio control access between a single Legacy VCS control site and multiple VoIP VCS control sites to the analog port of a single R-APC Resource. L-APC analog access connections to the R-APC are further illustrated in Figure 32.

1. The L-APC must simultaneously accept radio control signals from a single Legacy VCS and up to 6 VoIP VCS control sites.

The L-APC must provide radio control PTT preemption of the lower and equal priority control sites for a single Legacy VCS and up to 6 VoIP VCSs.

The L-APC must support both Legacy VCS and VoIP VCS connections.

The L-APC must simultaneously support both Legacy VCS and VoIP VCS connections.

The L-APC must provide radio control preemption of the lower and equal priority control sites for simultaneous VCS connections.

The L-APC must, in the event of a loss of communications with one or more control sites, maintain communications with remaining operational control sites.

Non-Priority Mode This section covers the requirements of the L-APC for granting radio control access to the analog port of the R-APC without PTT priority levels being assigned (i.e., all PTT priority levels equal).

1. The L-APC must, when control facilities have equal priority, provide a transmit voice path and PTT confirmation to that facility from which the PTT arrives first.

The L-APC must, when control facilities have equal priority, only allow one facility at a time to have control of the radios; subsequently, lockout the remaining control facilities, i.e., block the voice transmit path, PTT/PTT release, and M/S transmitter/receiver select capabilities of the remaining control facilities.

The L-APC must, when in “non-priority mode”, provide receive voice path continuously to all the control facilities.

The L-APC must, when in “non-priority mode” and upon release of PTT by the control facility that issued the PTT in progress, transmit a PTT release confirmation message to that control facility and terminate the lockout condition for the other control facilities.

The L-APC must, when in “non-priority mode” and upon release of PTT by the control facility that issued the PTT in progress, permit any previously blocked control facility, attempting to PTT, to acquire transmitter(s) without requiring the facility to release and reactivate PTT.

The L-APC must, when in “non-priority mode”, provide the option for the Legacy VCS to override PTT of all VoIP VCSs, regardless of which control facility arrives first.

Prioritized Mode This section covers the requirements of the L-APC for granting radio control access to the analog port of the R-APC with PTT priority levels being assigned.

1. The L-APC must arbitrate radio access permissions to all the connected control facilities based on their PTT priority levels.

The L-APC must, in an ED-137 multi-level PTT priority scheme (i.e., Test, Normal, Priority, and Emergency), permit the higher PTT priority facility to override the lower PTT priority control facility with respect to communicating on the frequency(ies) to which those control facilities have access.

The L-APC must provide a transmit voice path and PTT confirmation to the controlling facility when a controller at that facility asserts PTT.

The L-APC must, when PTT is active at a lower priority facility and a PTT signal is received from a higher priority facility, release the lower priority facility’s PTT control and lockout that facility while PTT is active from the higher priority facility.

The L-APC must, when in “prioritized mode”, provide receive voice path continuously to all the control facilities.

The L-APC must, when in “prioritized mode” and upon release of PTT…