23-21-00 SELECTIVE CALLING (SECAL) SYSTEM Back
A. System Function
A Selective Calling (SELCAL) decoder unit is installed with the Dual High Frequency (HF 1 and HF 2) system (Ref. 23-12-00)
Each aircraft which has a Selective Calling unit installed is assigned an applicable four-tone audio code sequence for automatic identification. A ground station keys the sequence when contact with that particular aircraft is necessary. The signal is received on the HF 1 system only and is decoded by the aircraft’s SELCAL decoder. The crew is alerted by an audible tone in the pilot’s and co-pilot’s headsets. The SELCAL indicator will also come on in the flight compartment and is set again by pushing the indicator.
B. Systems Components
The primary components of the system are the:
The system permits ground stations equipped with SELCAL tone encoding equipment, to call one aircraft by transmitting four aircraft-specific audio tones. When the correct tone sequence is received by the aircraft SELCAL decoder, an audio tone is sent to the HF 1 system only.
A Selective Calling (SELCAL) decoder unit is installed with the Dual High Frequency (HF 1 and HF 2) system (Ref. 23-12-00)
Each aircraft which has a Selective Calling unit installed is assigned an applicable four-tone audio code sequence for automatic identification. A ground station keys the sequence when contact with that particular aircraft is necessary. The signal is received on the HF 1 system only and is decoded by the aircraft’s SELCAL decoder. The crew is alerted by an audible tone in the pilot’s and co-pilot’s headsets. The SELCAL indicator will also come on in the flight compartment and is set again by pushing the indicator.
B. Systems Components
The primary components of the system are the:
- SELCAL decoder (Ref. Fig. 2)
- HF 1 transmit/ SELCAL switch indicator (Ref. Fig. 1)
- HF 1 controller (Ref. Fig. 1 and Fig. 4)
- Power amp/ antenna coupler (Ref. Fig. 2)
- HF antenna (Ref. Fig. 3)
- Receiver/ Exciter (Ref. Fig. 2)
- Bus adapter (Ref. Fig. 2)
- PA amplifier
- Dual external capacitor (Ref. Fig. 2)
The system permits ground stations equipped with SELCAL tone encoding equipment, to call one aircraft by transmitting four aircraft-specific audio tones. When the correct tone sequence is received by the aircraft SELCAL decoder, an audio tone is sent to the HF 1 system only.
.jpg)
.jpg)
.jpg)
.jpg)
.jpg)