The one marked TD71 is an OTIS Touch Tube used in elevators. It is a touch sensitive trigger tube. They are also named 425A5 or 2040. They are similar to the RCA 1C22.
The 71 in TD71 is probably the voltage drop when triggered. You had to replace tubes with the same voltage drop to get the circuit to work properly. I’ve seen voltages from 69 to 74 stamped on these. The other tube looks like a Geiger tube. /Martin -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+unsubscr...@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/3c4a6428-3a65-465a-9528-d8615a6c1cff%40googlegroups.com.
