The Interlock is an equipment designed to be used by contesters where they need to check, supervise and limit, how many radios are in transmission at any given time.
There are contests where you can participate as a Multi/Single where a single signal may be present in an instant in the air; or Multi/2 where you can have a maximum of 2 signals simultaneously in the air.
The Interlock is responsible for overseeing just radios are in transmission and can block the radios that require it. For this it is necessary to connect 2 signals between each radio and Interlock: PTT and Inhibit. With the PTT the interlock detects which radio is in transmission through the Inhibit, the radio can be locked – in case it’s required. Radios as Yaesu or Elecraft (K3/K4) – that support this inhibit signal – are easy to interface with the Interlock, since they are Plug & Play.
Other radios do not exhibit this signal, can also be used, but in these cases should do pass the Key signal – CW – or microphone signal – SSB – through a box with relay; in stand-by the relay passes the signal to the radio, but when activated prevents the signal from the radio so then there will be no transmission. It’s available the Aux Box for those equipments that don’t include the inhibit signal as Kenwood or ICOM.