Three for the price of one seemed, on the face of it, a sensible way to start expanding the basic unit. It occurred to me it was time for some ambition to come to the fore. Expansion to the basic unit by the fitting of what I believe is known in the trade, and the world of slick and competent computer users, as an Add-on.

I was rather taken with the idea of a Mouse and a Joystick as it seemed to me these would quicken my journey into unknown areas such as graphic art and games where access to icons and fire buttons held promise of improved reaction time. Where to start was the next question. The instruction at the rear of the Welcome Guide offered some advice, though it's somewhat sparse. I would be able to provide greater precision to applications, particularly those requiring a two dimensional application. I hesitated, what did this mean, what was I letting myself into?

Further reference to the manual enabled me to locate the Mouse/Joystick port. More importantly I found reference to the expansion connector on the side of the keyboard. If I could make use of this I felt certain the possibilities would be proportionally greater.

Enquiries led me to the Mertec Compact Companion Assembly. With a name like that, I was in business. The pack duly arrived containing the unit. It was a neat compact hollow wedge laminate containing a ROM, with connections to three ports. Two 6mm diameter screws are provided with which to bolt the unit to the keyboard. Note, if, as in the case of the screws I do provide some technical detail it is because such information has been provided. The instructions came as four photocopied sheets stapled together in one corner. I've heard of keeping the costs down but this is stretching things a little. I found the instructions for fitting clear and precise (except for the left and right hand bit). The accompanying diagram was a very useful adjunct.

The unit is neat and when fitted unobstructive, the cream dappled finish matching the Compact keyboard quite well. The single lead from the unit fits snuggly round the back of the keyboard, plugging into the Joystick/Mouse 9 pin D-type plug.

Fitting the unit, I must say was extremely simple. All one needs is a medium size screwdriver, and a modicum of intelligence and common sense. The authors are adamant the Compact must not be connected to the computer power supply whilst the unit is being fitted.

Having undertaken the simple task of disconnecting, one turns the keyboard over to find the PCB on the righthand side. This is the printed circuit board and is referred to as the expansion connector in the Welcome Guide. I am still trying to fathom out why or how it should not be in the same place if I was left-handed. As it happens, it doesn't really matter as the prime task is to gently push the Companion, after having lined up the gold contacts of the gold connector with the silver tracks, onto the PCB. This required no more than a little even pressure.

Next insert the two screws through the fixing holes, clearly visible in the black angle bracket, and push home. If any difficulty was experienced, it was now with the need to ease the white connecting cable to one side to allow the screws to slot into place. At this stage, only tighten the screws so as to ensure the unit will not slip and slide. Connect the white lead to the D-type plug at the rear of the keyboard and re-connect the whole to the computer.

The Menu Options are:

Table 1

Switch on, if all is well the message on the screen will show in addition to the standard message Mertec Companion. Switch off, disconnect, and tighten the fixing screws. If, however, you do not get the message, disconnect, turn the keyboard over and very gently slide the gold edge connector to the left or right as required. It is most likely only the very slightest adjustment will be needed. Connect up again and check the system. If power-up is correct, tighten home the two screws, after switching off and disconnecting.

I have emphasised the importance of isolating the unit from the electricity supply because the manufacturers do so with considerable emphasis, and I believe in safety. Anyway if, by not obeying the instructions, you blow the whole unit, no comeback!

The user of the Mertec Compact Companion is offered three outlets, the Joystick or Analogue port, the User port and a 2Mhz Bus port. This is to say where one had two before fitting, now there are three.

Preliminary Specification tells one there are three commands in the Companion software. These are CMENU, CSTATUS, *CSETUP[RB]. To obtain assistance the software will respond to *HELP followed by one of the above commands, which the authors term CLI Commands. All these commands can be abbreviated as long as the minimum is sufficiently long to ensure the correct command is executed. Apparently other software present in the machine could conflict, and the impression I had was one of trial and error. If command conflict does occur, revert to the full name or precede the command with an extra "C", e.g. *CCMENU, "which" one is informed by the Preliminary Specification "may help to reduce the problem".

*CMENU displays a ten choice menu. Eight of the options directly control the setting of bits in the configuration byte, while the remaining two allow the user to exit the menu either maintaining the most recently revised menu or not. Each option is either operative or non operative, different nomenclature being used depending on the function of the option. The choice is made by use of the cursor keys to position a white bar on the option, then pressing the Spacebar or RETURN, both of which act as a toggle "on/off". Having moved around the menu making the required amendments, the operator moves to option Exit and presses RETURN. A message is then displayed in a window overlaying the menu configuration, offering the choice of the amended menu becoming the default menu or default remaining at the menu existing prior to the most recent amendment.

*CSTATUS followed by RETURN displays the current and default configurations in three forms, Binary, Decimal and Hexadecimal. I am sure it is no coincidence that the number of options, other than the 'exits' coincide with the number of bits of a configuration, namely eight. I am certain for the technically minded such information will be most useful. Table I indicates the relationship between option and byte.

*CSETUP provides the facility to use the chosen configuration within a program. This statement is qualified in the instructions by "where appropriate". The entry in the program can be in either of the three number base forms. All three CLI commands need to be used in conjunction with each other to be most effective.

A useful key in the early stages of use, and if you happen to lose the written instructions, is TAB which, when pressed provides, in a window, information about the option in question. Similarly TAB used outside the CLI. command mode provides instruction as, to how to use.

The "Preliminary Specification" is dotted throughout with technical information, which if still rather a novice, does leave one a little non-plussed. I am assuming at this stage things will be come clearer as time goes by and the Companion is put to 'full' use. Meanwhile I must live in ignorance of the niceties of *FX 16,0 and the resulting effect on the interrupt overhead.

The claim is the Companion does not make use of user memory except when in MENU mode. The "safe" area of non-screen ram in the &7E00-$7E0F is used.

The software makes use of the extended vector (IND3V) which with the Osbyte vector (BYTEV) enables Osbyte calls to be intercepted when ADC is in use. Care is also countenanced if additional ROMS e.g. PMFS, or FX 22, FX 23 or similar are written into your program.

ROM polling (?) apparently, and I am in no position to dispute it, occurs at centisecond intervals. Similarly, an Interrupt is intercepted as "unrecognised Interrupt" ROM service call 5, after indirecting via IRQIY but before IRQ2V. It also signals an ADC "End of conversion" which allows for handling the Mouse.

The owner is also provided with an example Mouse program, yet to be tried by yours truly.

It seems to me I have an add-on which has several avenues down which I might well be able, in the fullness of time, to venture.

I do know that care has to be practised now the Companion is fitted, as far as it is possible so to do. Some hiccups have occurred when I have been using View Professional without making certain the Companion is disabled.

I hope to do a fuller report on using the Master Compact with Mertec Compact Companion Assembly, I hope not a monster attached. I did encounter problems with an AMX mouse on the user port, a tap or knock producing some weird results even with the Companion disabled. I am always cautious of making criticism when I am uncertain of the cause for so doing. In this case it seems to me the instructions could have been a little more explicit for the less technically-minded.

There are those of us who wish to get on and make use of the equipment we possess rather than be cluttered up with technical detail. Clearer pointers as to what is the most suitable combination of options from the main menu for each of the ports it seems to me would be most useful. Certainly, at the moment it is a matter of trial and error.

The Compact Companion costs £39.95 inc VAT and is available from Mertec, 35-36 Singleton St., Swansea SA1 3QN & (0792) 467980.