The current trend is for many of the functions of radio equipment – even down to the control buttons on the front panel – to be software controlled. In one manufacturer’s equipment the only screwdriver-adjustable control is that for setting maximum deviation; this is insisted upon by the Radiocommunications Agency for use in the UK.
Software control enables radio sets to be cloned so that once a single piece of equipment is programmed with its frequencies, power output, selective calling, etc., the whole of a fleet of mobiles can be identically programmed in a short time. Some of the functions can be programmed by the user, but not all, and different manufacturers permit different degrees of programming.
The functions are allocated degrees of priority which determine which functions can be changed by each class of person. Again, some of the priorities may be altered by the user but the highest priority functions are installed in a programmable read only memory (PROM) by the manufacturer and can only be altered by replacing the PROM, in most instances a job for the manufacturer.
The essential equipment for major reprogramming is an IBM or equivalent computer and the equipment manufacturer’s software which is supplied as a package complete with hardware interface and instructions.
Cloning may be carried out using an inter-connecting cable between the equipment, or restricted reprogramming via a unit supplied by the equipment manufacturer for the purpose.
The functions which may be programmed from a computer are:• Channel frequencies.
• Transmitter power and deviation.
• Receiver squelch setting (referred to Sinad ratio). Selective calling details including encode or decode only, type of signalling, extension of first tone and call sign.
• Transmission time out timer.
• Channel busy light. Transmitter inhibit on busy channel.
• Alert tones. Tone decoder indicator.
• Low battery indicator. Battery saver.
• Channel frequencies, including any offsets.
• Lock out of any channels.
• Channel spacing.
• Channel search priority.
• Frequency stability.
• Signalling type.
• Control functions.
• Synthesizer reference crystal (the frequency can be trimmed to compensate for ageing).
• Transmitter power.
• CTCSS (encode and decode).
• Timers.
• Alerts.
• Code number.
• Alert tone/vibrator/repeat.
• Urgency.
• Out of range warning.
• Printer on/off.
• Language of display.