Leave your home safely in the hands of the Radionics CNS, says Brendin Lewis

With the current proliferation of microcomputers in both homes and business alike, one aspect of computing is all but forgotten. This is control, i.e. the ability to control various devices around the home, business or wherever.

The Radionics CNS goes some way to fill this market, where other manufacturers offer only add-ons. Both sensing and control ports come as standard allowing control of devices ranging from robotic arms to the garden hose.

Add these facilities to a machine which is TRS-80 Model 1 compatible (plenty of freely available software) and we may be looking at an interesting product. Nor is expandability forgotten with printers, disk drives and RAM expansion available immediately.

Working from first impressions it seems that this machine is aimed at two main sectors of the market, these being the electronics dabbler and the education sector, where I feel the system could do well.

I must admit that when I first set eyes on the beast, that's exactly what I thought it was, a beast. It is certainly not the best looking machine on the market, but as the old saying does, you can't judge a book by its cover.

When you take a closer look at the system, its good points become apparent. It has a metal base which gives the machine a good measure of rigidity and also doubles as a heatsink. All connectors are mounted either on this metal base or directly on the pcb (printed circuit board), which in my view is not a good practice as the constant plugging and unplugging does put stress on the board. There are advantages in doing this though. The system is easer to assemble, and this and other reasons keep costs down thus giving the machine better value.

Nothing is marked on the casing to describe the various connectors and it is virtually impossible to guess what most of them do without referring to the manual. The manual starts with setting up the machine, which helps a bit.

The keyboard has a total of 57 keys including four cursor keys and two function keys. The positioning of these keys seems a little strange at first but one gets used to it fairly quickly. In use the keys are excellent and typing is comfortable. By today's standards, 57 seems very few, but as with many things simpicity can be an advantage.

The unexpanded system uses cassette-based file storage, the cable for which is an integral part of the machine. This is probably to prevent people plugging a normal lead into the control ports, as these use standard 3.5" jack sockets. Though clamped to the machine, the lead is easily removed when a disk expansion is fitted.

The system on its own uses only 5 volts to control external devices. If mains voltages need to be swtiched Radionics supplies the Mains Switching Unit which gives control of devices up to 1500 watts (approx 6 amps) rating. This is a standard, dual mains outlet which contains a transformer and a relay for each outlet. These relays are energised by the control signals from the computer via the jack leads.

The unit works well except when first powered up: in fact, when I powered the unit up the computer reset itself, as did the TV set.

This is caused by powering up the small transformer without a load applied.

Two manuals are included with the system - a user guide and a project manual. Both are of high quality in print, paper and presentation.

The user manual contains a section explaining the machine's Basic, which seems accurate and is clearly presented. The section on control and sencing has lines through it and tells you to refer to the project manual for details. If this information is of no use, what is it doing in the manual?

The final section of the manual contains the circuit diagrams and an overlay of the PCB, or at least it should. What it does contain is an overlay of a different revision pcb, and circuit diagrams of the control, sensing and printer interfaces are missing.

The project manual on the other hand contains descriptions of how to use the six control ports and the four sensing ports. This includes the addresses which are used to switch devices on and off. A short section also deals with using the sound facility through the internal speaker.

Following this, eight separate projects are described in detail with instructions on how to construct the various bits of hardware and lists the software required to run on the system for each project. The projects include a favourite TV programme finger, a garden hose monitor, a smoke alarm, a house plant waterer, home security lights, wind and moisture indicators, a burglar alarm and a disco light controller.

Most of these projects are made up of household bits and pieces with the addition of freely available electronic components like solenoids and LEDs. For this reason, all projects could be tackled with confidence by any novice.

Owners of the CNS are eligible to receive the CNS Club Newsletter which promises to bring news of projects from both the Radionics workshop and from other CNS owners. This is an appealing idea and makes for good owner/manufacturer relations.

Even though the CNS is designed for users to build their own interfaces, the system does have a few of its own. It is possible to expand the 16K RAM up to 48K; 16K plugs directly into the pcb while the other 16K is fitted to a 'piggy back' board which fits above the board-mounted memory. A disk controlled board can be internally mounted to the roof of the case, with the option of a double density controller that plugs directly into the single density controller.

Printers can also be fitted, with a Centronics type interface already built into the system, though it seems that this printer will only operate from within Basic. Another interface is required when using the system with the DOS because the printer controller is the same as that used for the control and sensing ports and would therefore be configured at the wrong I/O port for the DOS.

Expansion of the control and sensing section of the machine is also possible with the number of control ports increasing from the standard six up to a total of 255. The control ports are expanded externally, whereas the sensing ports can be expanded from four to 22 internally.

When powered up, the screen displays random characters because the system does not do a power-on reset. I find this incredible as the circuit to do this is so simple that it should be fitted to every machine as a matter of course. On this system the reset button (again unmarked) needs to be pressed before the screen displays 'Komtek micro system', and not Radionics as the manual states. Komtek is also marked on the printed circuit board, so who is Komtek?

The Basic used on the system is standard Microsoft level 2. Due to this and other small details, the CNS is compatible with the TRS-80 Model 1 and the Video Ganie models 1 and 2.

No software other than the resident Basic was available with the review machine, so I contented myself with tapping in some of the Basic programs from the manual. There should be no problems obtaining software for two reasons; the first is the machine's TRS-80 compatibility and the second stems from the version of Basic being used. Being Microsoft Basic it makes the system semi-compatible with a whole range of other machines, from which software conversion should require a minimum of effort.

One thing I learned by typing in the programs was that the sound facility didn't work, from within Basic at least. The other thing I found was just how easy it is to control an external device with this machine. One memory location in the system is mapped to the control ports. Within this one byte the six least significant bits are used, one for each of the ports. When the relevant bit is set to 1 then that port is switched on; if set to a 0 it is switched off.

The best way to describe the use of the control and sensing facilities is to give an example, so the following section briefly outlines two of the manual's projects.

The smoke alarm hardware is of a simple design. Using a plastic tube with a hole drilled in the middle of it, one end is fitted with an LED and the other with an LDR (light dependent resistor). Under normal conditions (i.e. smokeless) the LED would light the LDR and a constant, known output is present. When smoke enters the light chamber the light reaching the LDR is reduced and thus the output changes. This output change is sensed by the computer and the action taken is to switch a control port on. This port would be connected to some form of alarm. This project is controlled by a program contained on one side of A4 paper.

Another interesting, and again very simple, project is called home security lighting. This type of device is already used in many homes to prevent burglary. All it does is switch lights on and off occasionally to give the impression that someone is at home. This project uses the Radionics mains switching unit to switch the mains voltages.

Two methods of control could be used for this project. The simplest method would simply switch the lights on and off randomly by interrogating a random number generator; the problem with this system is that the lights turn on and off erractically, which is unnatural. The other, more efficient system uses the inbuilt real time clock to switch the lights in a given order and at a given time. Thus, this system could simulate a person going to the kitchen and then back to the lounge by switching on a kitchen light, leaving it for a time and then switching it off.

Due to time constraints it was impossible to test any of the projects from the project manual. I did, however, make up a little test of my own based on one of the published projects (the TV timer). Being a keen cricket fan, I wanted to keep in touch with the score from the television. So I wrote a small Basic program to set the clock and then switch the TV on for five minutes every half hour during the afternoon. This was very successful.

It's all very well to talk about computer control, but without some sort of feedback from the device being controlled, the control is almost useless. For example, my TV switch on/off would be of no use if no power was applied to the mains switching unit as the computer would still think it has switched on the TV. This is where the sensing ports come into their own because these actually produce the much needed feedback.

The sensing ports work on a very simple principle of short/open circuit, i.e. if the two sense wires are shortened together then one bit within the system is changed and can be acted upon. This bit is tested in much the same way as the control ports. One byte in memory is set aside as the address of the sensing ports. By looking (PEEKing) at this address, it is possible to find which port or ports are active. The four high order bits in the byte are mapped to the four sense ports and are normally at logic 1, but if a port is activated then its value changes to a 0.

The system of control and sensing mentioned above is fined, provided that you don't really want to control various devices throughout a house. Problems arise when separate cables for both control and sensing need to be run to each location. This process will prove untidy unless they are installed when the house is built or rewired.

There is another method of controlling devices around the house which, as far as I know, is not available for the CNS. This system uses the existing mains wiring to communicate with the devices by modulating data signals onto the 50Hz mains signal. This type of system is known as a broadcast system because all devices connected to the mains would receive the data. Therefore, all devices need a separate identification number so they only respond to commands meant for them. This type of system is more expensive than the simple relay type switching because electronic decoders need to be fitted to the mains sockets.

Certain precautions must be taken with this type of system because of the hazards of using mains voltage. All of the encoding and decoding electronics must be suitably isolated from the mains supply and a filter must be placed at the mains inlet to the house to prevent the modulated data signals from escaping to other houses. Otherwise they could cause interference on radios and TVs. Also, if a neighbour uses a system similar to yours, some of his devices may be activated by your signals.

Thought not the best presented system available, the fact that the control and sensing ports are fitted as standard and are so easy to use makes the machine an ideal educational tool. Not only in schools and colleges, but also for anyone interested in learning about some of the principles of computer control.

TRS-80 compatibility gives the machine a large, already established software base. It also offers an easy upgrade path from the basic cassette filing system to the full double-density disk system. Taken together, this and the range of services provided by Radionics result in an interesting product which is reasonably good value.