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APPENDIX C

GROUND-TO-TANK COMMUNICATIONS

1. GENERAL. The requirement for light infantry soldiers on the ground to communicate with a tank crew in an operation was a significant and reoccurring observation made during this rotation. The C-2296 VRC Intercom Control Unit mounted to the back of the M1A1 tanks proved to be instrumental in supporting this communication requirement. The C-2296/VRC Intercom Control Unit can be described simply as the fifth intercom control unit in the tank intercom system. The only difference to this intercom unit is that it is located outside the tank rather than inside as are the other four units.

The external intercom control is mounted on the right rear of the M1A1 tank between the grill door and right stop light. An ammunition can is used as an external phone box at this location and wired to connect the external intercom system. This affords the phone some protection from dirt, weather, and external hazards. External binding posts are added to the external system to allow soldiers to include the tanks in a company or platoon "hot loop" of field phones.

2. INSTALLATION. Install the interconnecting cable between the tank driver's C-10456 Intercom Control Unit and C-2296/VRC Intercom Control Unit.

• Route the cable from the C-10456 Intercom Control Unit located in the driver's position to the C-2296/VRC Intercom Control unit located in the right rear of the tank by securing the cable to existing cables using plastic tie raps.

• Route the intercom cable down and across the floor of the tank's hull through a spare grommet in the firewall that leads into the battery box.

• Route the intercom cable out of the hull through the hole used for the tail-light wiring.

• Add a 10-ohm, half-watt, fixed resistor between pin four of TB61 and pin one of TB62 of the C-2296/VRC Intercom Control Unit to lower the receiver volume control. This should prevent possible audio feedback that may occur if the volume control is set on the maximum position.

• Add a second A-80 microphone amplifier assembly to the C-2296/VRC Intercom Control Unit to boost the audio from the handset. This is required because there is no C-2297/VRC Intercom Control Unit in the system to amplify the signal coming from the AM-1780 Intercom Amplifier located in the tank.

3. MODIFICATION WORK ORDERS (MWOs). Mr. Jack Jory, Logistic Assistance Representative (LAR) from the U. S. Army Communications-Electronics Command (CECOM), and the Electronic Section of the Directorate of Logistics at Fort Lewis, WA, designed a system to enhance the communication between the troops on the ground and the tank crews. This system was developed for local field testing only by trained personnel. Twenty tanks were successfully outfitted and tested with this intercom system.

Commanders may authorize special modifications of materiel. Materiel must be able to be returned to its original state within 24 hours. Special modifications to aircraft and COMSEC equipment require prior approval from ATCOM and NSA, respectively.

This system meets the requirements of AR 750-1, Army Material Maintenance Policy and Retail Maintenance Operations, Modification Work Orders (MWOs), paragraph 4-9f.

Appendix B: Tank Hazards - Extract

Acknowledgements