Ringing problems was [Asterisk-Users] TDM400P Revision question.

David Josephson
Wed, 20 Apr 2005 19:01:06 -0000

Rich Adamson responded to an earlier reply (not from me)

> Eric, those links have nothing to do with his stated problem. The
> problem is "105v AC on the pstn line when on-hook and no
ringing".

No, he says the issue is about ringing and strange voltages on his
Digium TDM400 FXS ports, not the PSTN line. He measures 107 VAC on the
line with the phone on hook and not ringing. Are we sure this is
measured across the line and not from one side of the line to ground?

If there were 107 volts AC on the pair, and there was any current
available, the phone would ring all the time. Since it doesn't, it's
likely to be a faulty meter or (more likely) a high resistance ground
fault in the PC power supply providing a sneak path for a few microamps
of power line voltage to get to the pair. Check grounding of the PC case.

The basic problem however is that (assuming the meter is right) there is
only 45 volts during the ring interval. This is not enough for most
ringers. Try boostringer=1 as suggested by the last response and check
the ring voltage then. Many ringers need at least 75 volts to function
properly.