SELCAL

GENERAL

SELCAL or SelCal, is an abbreviation for Selective Calling, is a HF (often with a lot of noise and distortions) or VHF mode of transmission (from the ground station) using a ground based encoder and a radio transmitter which selectively calls the particular aircraft cabin crews, via an aircraft based decoder and radio receiver installed in the aircraft.

SELCAL is basically incorporated in aircraft especially for the ease of the crew to respond to messages that is intended for that particular aircraft without the need to constantly monitor it.

Since HF channel is quite noisy due to interferences, the audio is muted.

Each alphabet carries its own frequency being spaced at a time interval of 0.5 second between two consecutive letters and dash (-) is being spaced with a time interval of 0.2 second.

Therefore the total time interval for one transmission of AB-CD, will be,= (0.5+0.5)+0.2+(0.5+0.5)=1+0.2+1= 2.2 seconds

LIMITATIONS

A SELCAL code might be designated to more than one particular aircraft but has to ensure they don’t operate in the same region or airspace.

Currently, SELCAL 32 EXPANSION PROJECT is under evaluation to increase the number of possible allowable codes.