The Dec., 80, issue of SYNTAX described how to wire a big keyboard onto your ZX80 or MicroAce. Some keyboards have up to 20 more keys than you need. You can wire these extra keys in parallel with existing keys to access shifted functions without pressing the SHIFT key.
If you have double pole keyswitches, just wire an existing key in parallel with 1 pole pair of pins on each extra key and wire SHIFT to the other pair.
With single pole keyswitches, use ICs to implement the permanently shifted keys. The circuit following shows three wired keys. To connect more, just use more 125’s and connect pin 8 of the 7421 to pin 1. Keep adding AND chips until you wire all the keys you need; we have wired 16 permanently shifted keys this way.
To relabel your new keys, use color-coded labeling strips with adhesive backing. Dry rub-down letters make professional-looking labels for covered key tops. You can also use these to label BASIC commands on the front sides of the keys. A coat of lacquer protects key tops from wear.
