I have, over the past few months, had an opportunity to use the Compudex telephone dialling system designed and produced by John Brumbach (Compudex, Inc., 7736 N. Harlem Avenue, Niles, Illinois 60648). This system is a hardware/software add-on for the ZX81/TS1000/TS1500 which stores as many telephone numbers as you have room for and calls any one of those number for you on command. It sells for $89.95.
The hardware
The board, 4.5 by 8 inches, fits on the rear of the computer like most other devices and has: an extension on the back for additional peripherals, It is compatible with any combination of printer or memory (including the Hunter NVM board).
On the board are two modular phone plugs ~~ one is connected to your telephone and the other goes to the phone line with a modular cord (supplied). The modification to your phone system is completely transparent when the computer is off(i.e. use the phone as you normally would without complications).
There’s a miniature loudspeaker on the board through which telephone signals (dialing, ringing, speech, etc.) can be monitored before picking up the receiver. The rest of the circuit (six IC’s line isolation transformer, and a few discrete components) deals with tone detection, tone generation, and output port selection. The board is single-sided and well laid out with a few jumper wires. In the production model the board could well be reduced in size.
Two potentiometers allow adjustment of speaker volume and sensitivity in tone detection. The latter is very difficult to adjust when the system is plugged in and running — the RAM pack gets in the way of your screwdriver. A vertically mounted pot would be much better. (Note added: John Brumbach tells me that the potentiometer will be replaced by a more sensitive vertically-mounted one.)
The software
The program is written in BASIC with some machine code routines. After loading without difficulty (2 minutes) the display shown in Figure 1 comes up on the screen.
Possible responses are: A: to redial a number (shown on the screen); B: to enter a number to call in “immediate mode”; C: to call a number specified by a code such as POLICE or MOM; E: to edit a directory; L: to display the primary directory; S: to display any directory; Z: to save the program and directories on tape; +: to add a directory; and finally, $: to dump the program and data into the 8-16K region.
Most of the routines work as you might expect, The dialing is superfast and has to be heard to be believed. Automatic redial is an option if there is no reply (after about 8 rings) or if a busy signal is encountered, Entering ‘X’ from the keyboard will interrupt the dialing routine at any time.
One of the first things you do with the unit is to enter a directory of 22 phone numbers and in order to do so you would answer “+” form the main menu, After some pron ts and answers a ruler scale is presented. You then enter the number followed by an identifier for your own convenience. An example is shown in Figure 2.
It’s disconcerting to see the number disappear on hitting ENTER — you have no idea what the directory is going to look like until you’ve entered all 22 numbers (or blanks). So remember the format.
To make a phone call you load the program, choose “L” or “S” and then the letter corresponding to the number desired. You can also enter numbers directly. The progress of the call can be monitored on the loudspeaker so there’s no need to pick up the receiver until connection is made. It’s almost essential to have the program and the directories permanently loaded — no one wants to spend 2 minutes loading a tape simply to dial a 7-digit number. In these days of $15 TS1000’s it’s worth having a dedicated computer,
The BASIC program is quite easy to follow and customize for your own requirements. For example, you might want to use the unit to make calls through MCI and have the MCI tone recognized automatically. You might also wish to have the screen cleared before being prompted for entry of a number or code. You can also choose between normal and inverse video. Such modifications are easy to make, The unit is certainly recommended for those of you who do a lot of telephoning -~ it surely beats having to enter the 22 numbers for an MCI call.