Equipment Characteristics, Capabilities and Features

TM 11-5820-477-30

1-7. Equipment Characteristics, Capabilities and Features

The AN/GRA-39(*) is used in conjunction with a radio receiver-transmitter or a local battery switchboard to expand

the interfacing capability of the radio or switchboard. When connected with a radio, the AN/GRA-39(*) enables the

operator to transmit and receive voice frequency communications through the radio for a distance of up to two

miles (3.3 kilometers) from the radio. When connected with a switchboard, the AN/GRA-39(*) is used 10

accomplish net radio interface (NRI), by which voice communication is established between a field telephone

(switchboard subscriber) and a radio. In either application, communication can be initiated by the remote control

unit operator or by the local control unit operator. Transmissions initiating at the local control unit do not involve

the remote control unit. However, transmissions initiating at the remote unit require the presence of an

appropriately set local unit in the system.

When a handset is connected to both the local control unit and the remote control unit, two-way communication is

possible between the two units independent of any radio or switchboard in the system.

The local and remote control units are battery powered. The two units have identical battery requirements. Each

control unit has a waterproof case, and each has two D-rings for attachment of a sling which allows the unit to be

carried or hung on an appropriate object. All operating controls on each unit are located in the front panel.

Identification of the components of each radio set control group covered by this manual can be found in

TM 11-5820-477-12.

1-8. Description of Major components (figure 1-2)

Item

Description

1. Local Control Unit

Has a control cable for direct connection to a receiver-transmitter and a 5-pin

AUDIO connector for attachment of a handset, when required. Two LINE binding

posts on front panel permit connection to remote control unit for radio operation,

or to remote and switchboard for NRI operation. A-, B- and C- models have a call

lamp to signal incoming calls, and RFI filtering capability.

Has a 5-pin AUDIO connector for attachment of a handset (radio operation) or

2. Remote Control Unit

connector for jumper wires to switchboard (NRI operation). A built-in

loudspeaker allows operator to monitor calls in progress. Two LINE binding

posts on front panel permit connection to local control unit for radio operation,

or to local and switchboard, for NRI operation. A-, B-, and C- models have a call

lamp to signal incoming calls, and RFI filtering capability.

Allows operator to communicate with other parties in the system

3. Handset

1-3