The SELCAL is designed to detect the four letter code attributed to an individual aircraft, avoiding permanently monitoring the receivers.  When a call is identified for the aircraft, the decoder actuates a signal indicator which may be a light, a chime, or any combination of such crew alerting devices, and enables swift and reliable answering of the call.

This system operates with existing HF and VHF ground-to-air transmitters and receivers.  As a standalone unit, Cobham's SELCAL is well suited for upgrade programs in which function is not included in the Audio Management Unit (AMU).