Digistop 710 stop-watch timer

This stop-watch timer sports 6 Hitachi CD61 nixie tubes. It dates from around 1970. Judging by the brand (“Luctor” from Baarn used to be a brand of school supplies) it must have been intended for school use, e.g. timing of experiments of some kind in a physics class.

There are two buttons at the front: one to reset the counter and a start/stop button. The connections to both buttons are avalailable on a 3-pin DIN connector at the back, probably intended to connect the timer to external switches connected to the experiment to be timed.

The technology is TTL, using a basic design. Inside are 6 SN7490 decimal counters and SN74141 decoder/nixie driver IC's. On the circuit board there is space for another 2 decimal counters, so it is possible to change this device into a nixie clock. There would be one disadvantage to this: because of the TTL technology used, the power consumption is relatively high (about 15 W). And I am not sure the power transformer is designed for continuous use. What is worse, is that the power supply is not stabilised. The designer must have been a truly optimistic person.