In the early days of home computing, one of the most talked-about areas of application was computer control. A common topic was security: switching lights on and off at random, and controlling sensing devices to activate a burglar alarm. Another favourite was environmental control, monitoring temperature for example and switching appliances on or off as required.

Theoretically, at least, it should have been an easy matter to put just about any electrical device under computer control but early control units had severe limitations. Most required an elaborate interface involving trailing wires, and none had the intelligence which is built into the Red Box system. Such devices also had to be permanently connected to the host computer, increasing the cost considerably, and relegating the computer to the role of a simple timer.

Red Boxes, developed by Chris Curry's new company, General Information Systems (GIS), takes a different tack and one which is so simple and obvious you may well wonder why it hasn't been done before. The Boxes plug into the standard 13 amp ring main and communicate with each other using a mains-borne 129 kHz carrier, a frequency set aside by the British Standards Institution for just such a purpose. The devices to be controlled plug into the Red Boxes and this takes care of the safety aspects (e.g. protection from the mains voltage) as well as removing the need for lots of trailing wires. They will operate over a distance of approximately 200 metres so you can scatter them liberally throughout a fair-sized mansion.

The starter system includes a Red Leader, a Red One and a Red Two. Red Leader is the master control unit and is equipped with its own 6502 based computer and 8K of RAM. All communication is directed through this unit. Red One is an on/off switch and Red Two is an infra-red movement detector. Red Leader connects to the RS423 port of your Beeb, and a terminal program downloads upon switching on. This is simply to allow communication between Red Leader and your computer; the actual control program runs inside Red Leader, not the host micro. The beauty of the system is that after programming Red Leader you can unplug your computer and Red Leader will monitor the other units and carry out quite complex sets of instructions on its own.

The system is very security conscious. New Red devices are introduced to Red Leader by their security number (quite a lengthy sequence of digits) of which there are over 16 million combinations. As well as making the system virtually tamper-proof, it will let several Red Box systems operate on the same wiring without interference with each other, or other systems. Once downloading has taken place - a matter of some fifteen seconds - a menu appears on the screen. You can use this to give the Boxes simple instructions, such as times to switch on and off, and one device can be made to control another. For example, the sensor (Red Two) could switch on an alarm plugged into Red One. You can also control and monitor the Red Boxes in real time (for example, remotely switching on or off a TV or a light - great fun), but the real advantage is that once set up, you can disconnect your Beeb and leave Red Leader to look after everything itself. Using the Beeb in this way makes set up and control of the Red Boxes very easy whilst keeping the cost of the Red Boxes down to a reasonable level.

Although you could probably set up a simple security system using only the menu, the possibilities expand enormously when you delve into Red Basic, the programming language for the Red Boxes. It is near enough to 'ordinary' Basic to ensure quick familiarity, but has several new commands for full control of the Red Boxes. I wrote a couple of small programs in a fairly short time.

Although the manual lists all the Red Basic commands, a little more help would have been welcomed, and perhaps some practical examples. In particular, it doesn't tell you how to get your program running in Red Leader before disconnecting from your Beeb - just press the reset button on Red Leader. I also had problems downloading the terminal program into my Master. Acorn, you see, saw fit to set the Master's RS423 default baud rate to 1200 baud, not the 9600 of a standard Beeb. Not GIS's fault, but I wasted a lot of time trying to track down this 'fault'.

Among the more interesting Red Basic instructions are EVERY, TELL and WHEN. EVERY is rather like a FOR...NEXT loop but provides a simple way of repeating a set of instructions at specified time intervals. TELL and WHEN could well be used together: WHEN one device sends a message (or signal) TELL another device to do something (switch on for example). There are several other commands and functions all designed to make the writing of your own control programs a relatively simple task.

Red Boxes go much further than simple on/off and timing devices. A lot of emphasis is placed on the security aspects and intelligence of the system. When messages are sent to Red Leader - say a sensor has been tripped - Red Leader acknowledges receipt of the message and if no acknowledgement is received the originating box repeats the message. Conventional systems would just send a single message, and leave it at that, and thus could fall foul of a mains spike, or whatever.

It is also worth mentioning the new Red Box modules under development. Of prime interest, I would suspect, to all Red Box users is a real-time clock which will fit into Red Leader. This will have a battery back-up so you can unplug Red Leader once it's been programmed and re-situate it. I think this should have been fitted as standard, but it will cost around £10-£15 as an extra.

We can soon expect to see analogue devices for temperature measurement and light dimmer control, window contact switches, pressure mats and an alarm. This will be battery-backed so once triggered it can't be silenced by unplugging it. Additional Red Ones and Twos cost £34.95 (plus £2 p&p) and it is hoped that the other modules will cost about the same.

The analogue devices will enable the most fastidious control over room and house temperature and lighting. Heating can be switched on and controlled while there is movement in a room (don't fall asleep watching TV) and you could even monitor and record the temperature of a room during the course of a day or a week and program your heating system accordingly.

Red Boxes have pulled together the technology for implementing a home or security control system, and packaged it so that everyone can use it. The only adverse factor I can see is the cost of fitting a house with Red Boxes, but with clever programming the system could control both an alarm and environment.

I think Chris Curry has another winner here: an affordable and eminently practical method of computer control. A matter for discussion in '81 - a reality in '86.