What is Selcall?

Selcall (Selective Calling) transmits a burst of five in-band audio tones at the beginning of each transmission. This feature is common in European systems. Sometimes systems using Selcall are referred to as CCIR or ZVEI, specific tone encoding schemes used in Selcall systems. It is believed that some European countries favor one or the other of these tone schemes.

In the same way that a single CTCSS tone would be used on an entire group of radios, a single five-tone sequence is used in a group of radios. The radio speaker turns on as soon as the fifth tone of a valid sequence is decoded and the speaker stays on until the carrier squelch detects that the carrier is no longer being received. At that point, the speaker mutes and the decoder resets. The receiver speaker turns off and remains muted until another valid five-tone sequence is decoded.

A similar tone format is used for one-way tone-and-voice radio paging in the US. It is informally known as Reach format.