Quote:
Originally Posted by AndiiT
One other thing to beware of is the fact that not all types of ringer will operate correctly together on the same line, this is mentioned in a lot of early BT instruction manuals after the event of the "Plug and Socket" system; An inductive ringer, such as a bell motor, and a Capacitive ringer, such as a tone calling device, may if connected to the same line, act as a notch filter at ringing frequency and effectively sink the ringing current causing poor or no ringing.
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Indeed... I've limited my calculations / experiments to telephones all using a type 59A bell-motor - and there are even differences in values between those! Theory is nice, but one must run tests on one's own line, as lengths, impedances, etc... vary so much.