hi and good afternoon. I am trying to interface to the telephone line using
an impedance matching transformer -  ETAL P3191. At the moment there are
only three part.

1. The transformer part that is suppose to bring the phone line to off
   hook
2. A ringing signal detector circuit
3. A double pole relay that is suppose to switch the telephone line to
   either Part 1 or    Part 2.

Based on the information i have, a typical telephone line will go off hook
when the impedance detected is around 600 ohm. Then the ringing signal will
be terminated. The problem is it does not goes off hook. I tried changing
different resistor on the secondary but no result. Any idea, please? Below
is the transformer circuit.

Tip                0.68uF
o----------------| |-------o--     --o------------------
                              S   S                    |
                              S   S                    |
                              S   S                 Resistor
                              S   S                    |
o--------------------------o--     --o------------------
Ring

I got this circuit from the datasheet. The original value of the cap is at
6.8uF. I replace it with 0.68uF because it is very expensive for a cap with
a rating 200Vac. at that value. Is that the reason for not being able to go
off hook?
Another question - the capacitor must be there to block dc and prevent the
transformer from being saturated. If there are no dc, how does it know that
the resistance is 600ohm?

thank you.

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