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Definition: Selcall
Definition: Telcall

SC51 - Selcall/Telcall/GPS internal module

Add Selcall, Telcall and GPS position reporting to almost any HF radio!
(use for Automatic Vehicle Location or Tracking with suitable software)


The SC51 is a small module designed for installation inside almost any HF radio to add the additional capabilities of Selcall, Telcall and GPS position reporting. The SC51 requires a microphone with a DTMF keypad to control it's functions locally or can be configured so that pressing a push button will send an emergency call.

The latest SC51 software version adds 10 memory locations for storing those commonly used Selcall or Telcall numbers. Call a number by pressing just three keys on the keypad! Pressing (for example) 3 # # will call the number (selcall or telcall) stored in memory location 3. Numbers can be easily added, deleted or called.

With the SC51 installed in your mobiles you will be able to carry out vehicle tracking and location using your existing HF network. A base station radio that is capable of receiving the GPS information is required. A suitable base radio is the Barrett 950 and a PC running the Internav software.

When connected to suitable radios the SC51 can also control channel scanning and audio muting while providing outputs for driving alarm relays as well as audio alarms.

SC51 - Available selcall types

Selcall type





Selcall - Transmit and Receive

Telcall - Transmit and Receive

Beacon Request - Transmit and Receive

End of Call (Hang-up) - Transmit only

GPS Position Report - Transmit only


GPS Emergency Location call - Transmit only


GPS Position Request - Receive only


Remote Radio Kill - Receive only


Remote Radio Un-Kill - Receive only*


* The SC51 can be Un-Killled by entering the Un-Kill Code on a DTMF keypad microphone connected to the SC51. When Killed the SC51 will inhibit it's PTT circuit while switching the Mute circuit on, thereby making the radio unable to transmit or receive.

Note: the SC51 requires an external GPS receiver unit to obtain the position data. The GPS data is extracted from the "RMC" sentence and the data must be in NMEA-0183 format using either TTL or RS-232 signalling at 1200, 2400, 4800 or 9600 bits per second.

The SC51 is easily programmed with a PC or a laptop via the GPS data port. Simply pressing the radio's PTT button while powering on will initiate the SC51 programming mode (at 4800 bps serial data).

Once in programming mode the SC51 can be configured by using the freely available programming software. Click HERE for a screen shot. See the manual for more details.

All interfacing to the radio circuitry is through a 16 way ribbon (0.1in) cable while the GPS interface is connected through a 10 way ribbon (0.1in) cable which can be be taken directly to a 9 way D connector (ribbon cable type).

Click here for radio modification details

Click here for SC51 manuals


Size: 2in (51mm) x 2in (51mm)
Power: 6 vDC to 14vDC at approx 30mA
Programming: With a PC via GPS data port (at 4800 baud)
Functions Available:

Mute Open/Close
Send Selcall/Telcall
Repeat Last Selcall/Telcall
Recall Last Caller
Send Hang-Up Command
Reset Alarms
Send Beacon Request
Send GPS Location
Send GPS Emergency Position

Outputs Available: Called LED
Voice PTT (Active Low)
Selcall PTT (Active Low)
Scan Stop
Scan Pulse
Transmit Audio and Alarm Audio.
Open collector transistor available for Latched Alarm and Horn Alarm Outputs (30V 100 mA max, active low).

Key Pad Programmable Encode
Codan or Barrett Selcall/Telcall on Transmit
Auto-select on Selcall/Telcall Receive.
GPS functions available in Barrett format only.

Jenal Communications design and manufacture a wide range of radio related devices including units which use the standard HF selcall and telcall signalling as used by Barrett, Codan, Icom and Q-Mac. Thousands of these products are being used all around the world by Governments, NGOs, Commercial organisations and Amateur Radio operators. We also manufacture a number of devices which use the common DTMF (or touchtone) signalling system.
Last modified: 23 June 2015.