ICL1900

Hmmm.. I remember the fluorescent lamp across the front to illuminate the printing, the column display on the KSR model (since you couldn't see where the carriage had got to as there wasn't carriage), and the wonderful keyboard. What a nice feel. It was, of course, electromagnetically encoded -- each key bar carried an I-core that fitted onto a U-core in the PCB. Pressing a key completed the magnetic loop, increasing the coupling between the PCB tracks. Each core carried a clock track and the aprorpriate data output tracks -- these occured in pairs, normal and inverted for each bit, each core had one or the other. The signals from each pair went to differential amplifiers in one of the ASICs I believe. I started out with a 75-column KSR and a 118 column RO. By moving parts around, I got the reverse (118 column KSR, 75 column RO). The only problems was that column display I mentioned. It wasn't fitted on RO models, and was either 2 or 3 digit as approriate on the KSRs. I fitted a red LED to the left of it, wired to the appropriate signal (the counter board could handle 3 digits, maybe with a link swap). Not original, but the chances of finding one of those 7 segment filament displays and its socket are close to zero. -tony