3TKR-750OPERATING FEATURES1. Controls and Functions1-1. Front Panel1 Speaker2 CH/STATUS DisplayTwo, 7-segment digits display the channel number or sta-tus.3 VOLUME controlRotate to adjust the volume.4 DC source switch5 Dc source indicatorLights green when DC source is applied from the DC13.6V jack (DC 13.2V jack on E type versions). Lights redwhen DC source is applied from the BACK UP batteryterminal.6 MIC jackConnect a microphone to this 8-pin modular jack.19 8 7 63 4 521 TX OUT jackConnect a TX antenna or a duplexer to this receptacle.2 CONTROL I/O jackConnect an external programming device or repeatercontroller to this DB-25 interface.3 FUSEInsert 15 A blade fuses into these fuse holders.4 RX IN jackConnect a RX antenna or a duplexer to this BNC recep-tacle.7 Programmable Function keysPress these keys to activate their programmable func-tions.PF1 key (left side) Default : None (No function)PF2 key Default : Repeat disable/enablePF3 key Default : TX disable/enablePF4 key Default : Take overPF5 key Default : Monitor on/offPF6 key (right side) Default : Channel up8 BUSY indicatorLights green while a signal is being received.9 TX indicatorLights red while transmitting.17 6 52 8 3 4 91-2. Rear Panel5 DC 13.6V (K type) / DC 13.2V (E type) jackConnect a 13.6 V (K type) or 13.2 V (E type) DC powersupply to this jack.6 BACKUP battery terminal7 TEST/SPKR jackTest input/output jack. Connect an external speaker tothis jack.8 Cooling fan9 Optional spaceFor external DC power supply, or duplexer, etc.