Selcal 32 Selcalcoder
The Selcal Coder is a selective calling unit for aeronautical telecommunication. It simplifies the build-up of radio contact from ground to air.
Selcal Principle of the communication process
It works very similar to a paging or telephone device. It's the same with Selcal, but it only has four digits (letters A-Z,1-9). With your phone you dial a number to make a connection with someone.
Selcal, or Selective Calling as it is more correctly known, is an automatic recognition system that is operated by a two-tone signal. Two letters are grouped together as a pair so that only two tones are required for one call, for example "AB "+"CD".
