On 05 Jan 2005 16:19:20 GMT, (WayneSallee.com) put
finger to keyboard and composed:

My telephone disconects on the first ring.
Sometimes it's the second or third ring, but it's shorting out on the ring.
What usualy causes this? so that I can fix it.

Most (?) telephones have a bridge rectifier on the tip and ring inputs
to protect them from polarity reversals. This bridge could be made
from discrete diodes. In normal operation only two of these diodes (A
and D) are forward biased. It could be that one of these normally
forward biased diodes (eg diode A) is shorted. This would mean that
the phone would work OK when making calls (DC current) but not when
the line is ringing (AC current). During the negative AC cycle the
defective diode A would form a S/C with diode C.

A
Tip o-|-|-||---|-o +
| |
| B |
|-||-| |
| |
|--||--)-|
| C |
| |
Ring o-|--||--|---o -
D


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.