erco77 / 1a2-pic Goto Github PK

Scott Bonk [SN# 0020] noticed this on 09/21/19.

Supporting rotary was a recent feature to support dialing on the ICM line, and oddly I never thought to test with the CO lines to see that problem Scott reported this morning.

Fortunately it should be an easy tweak to the CPU1 firmware.
Cause: line detect used to control the lamp because I wanted the line lamp to reflect the actual state of the line, and not light if the line was dead.

But unfortunately that also means since rotary interrupts the line as it does, the lamp reflects the momentary breaks in line detect as the line going "dead".

It would be easy to have the A lead force the lamp on even if line detect drops out; very simple code change. But that would disable the line lamp not lighting when the CO line is dead even if a line is selected.

To solve, I /could/ use a short timer that keeps the lamp lit for an extra ~200ms when turning off, which would bridge the gap between rotary flashing, but still would go out if the CO line went dead. But as some pointed out on the Facebook group "Bell Telephone of the US and Canada", apparently original 1A2 systems the lamp would light even if there was no line detect. And this was probably to allow "flashing the line" with the "RECALL" button wouldn't make the line lamp go out. In which case loosing the "lamp goes out when line is dead feature" might be necessary.