ark@alice.UUCP (Andrew Koenig) (08/12/85)
> The former method has the advantage that there are fewer connections to > make when setting up the intercom, and thus fewer wires strewn around > the cockpit and fewer connections to give problems. But you *have* to > use portable PTT switches with it. The latter method is more > flexible. If the aircraft is already equipped with yoke-mounted PTT > switches, you can simply connect the mike cords coming from the > intercom into the jacks intended to be used by the headset mikes and > then use the yoke-mounted PTT switches. If only the left yoke has a > PTT switch, you can use it and mount a portable one on only the right > side (provided the aircraft has an AUX MIKE jack). Since I'm not > particularly fond of portable PTT switches, I decided to look for this > latter type of intercom. For a fairly nominal charge, Sigtronics will modify their intercom so that it will interact nicely with a yoke-mounted PTT switch. If it is not so modified, anyone who is talking when the switch is down will transmit. If it IS modified, pressing the PTT switch will connect the pilot's mike to the transmitter and shut off everyone else's mike. A toggle switch decides whether the pilot is the person occupying the left or the right seat. A second toggle switch allows you to select whether you have a yoke-mounted PTT switch or a portable one. If you do not want to pay for the modification, Sigtronics will (or at least would when I bought mine) send you sheets describing how to make the modifications yourself. > In some sense a no-frills Telex. Only controls are on/off, > volume, and squelch. No provision for tape input/output, > battery power, or anything else. Designed so that pilot's > headset is connected directly to the radio when power switch is > turned off - provides some failsafe protection, but pilot must > remember to turn the switch off if intercom power fails. You do not need to turn the switch off if intercom power fails. There's no relay or anything like that: the headsets are always coupled directly to the radio for receiving, period. You use the radio's volume control to determine how loudly the radio plays in your headsets. You use the intercom's volume control to determine how loudly the copilot's and passengers' voices are transmitted.