Can anyone tell me why I would get an extreme amount of hum/noise on my non-1A2 telephones if I have one of the 2565's off hook when picking up a "standard" single line phone?
All the 1A2 keysets are 2565 desk models, with the exception of one cuckoo clock.
The "standard" phones consist of a wall mount rotary, a wall mount trimline, and a (I really don't know the model on the next one, but it's identical to the one that used to be on the Johnny Carson show, basically a phone in a wooden enclosure). Oh yeah, a payphone also, but unplugging it completely doesn't help either.
None of them (with the exception of the payphone)date past '75 - '76, and the hum is present regardless of which one I pick up - until I put the 2565 back on hook.
Also it happens regardless of which 2565 I first pick up.
All the standard phones are home run and connect to the CO line before the KSU.
My only guess is there is some sort of backfeed when a 1A2 is off hook, and the "standard" phones need to connect after the KSU instead of before it, but I think that's a bad guess.
Is this where a diode block would come in?
TIA for any tips -
Thanks
Matt
