TM-9-2350-311-10 M109 Operator's Manual for M109A2, M109A3, M109A4 and M109A5 Download
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TM 9-2350-311-10 2–17 OPERATING AUXILIARY EQUIPMENT — CONTINUED 2-17.2 Radio and Intercommunication Equipment — Continued b. Amplifier AM 1780/VRC 1 The amplifier AM-1780/VRC is the master control for the intercommunication system. Nothing works until both vehicle MASTER switch and amplifier AM-1780/VRC are turned to ON. Before starting vehicle engine, make certain MAIN PWR switch and amplifier AM-1780/VRC is set to OFF, Otherwise, engine start could damage amplifier AM-1780/VRC. 2 With vehicle MASTER switch (1) to ON, set MAIN PWR switch (2) to INT ONLY and POWER CKT BRK switch (3) to ON. POWER lamp (4) should illuminate. 3 Leave INT ACCENT switch (5) at OFF, RADIO TRANS switch (6) at LISTENING SILENCE, and INSTALLATION SWITCH (7) at INT ONLY. 2-253