Intercommunications Set Control
The Intercommunications Set Control (ISC) provides each crew member with receive and transmit access to assigned radios and intercom channels

The ISC contains the controls to monitor radio and intercom channels, adjust each channel volume independently and select transmit channels. Receive audio is selected and volume level adjusted by ten identical control knobs. Each control is a rotary switch with seven detent positions providing attenuation from 0 to -20 dB in 3.3 dB increments. A master volume control provides an additional overall composite audio attenuation range of 30 dB. A seven position rotary transmit selector switch provides for transmit selection of intercom and radio channels. A three position ICS switch selects the keying mode. HOT MIC enables continuous keying on the intercom net PTT and permits the external PTT to key the appropriate channel. CALL is a spring loaded position which keys the emergency CALL intercom net. In the normal mode, the operator can select a radio for transmission, press the Radio PTT and talk on the radio, or press the ICS PTT and talk on the NORM ICS net. If a single cordset PTT is used, the PTT will follow the transmit selected position requiring the operator to select the desired radio or intercom channel. With a radio selected and the ICS switch in the HOT MIC mode, the operator can talk on the NORM ICS net. With the external PTT pressed, the ICS transmission will be automatically interrupted and voice transmission will be transferred to the selected radio. The CALL position has priority over other keying and provides direct access to all other crew members at an enhanced volume level, adjustable only by the listener master volume control.