vinodquilon
Member
Find the attachment of DTMF decoder (Activating an Electrical Device via Dtmf Telephone). I am using OEP1200 600/600 as the isolation transformer.
It has the property of blocking DC current through windings.
On detecting first ring voltage, BC547 will turn on line-relay to close line L2.
I have the following 2 doubts,
1. On turning on the line-relay, the resistance between the two lines L1 & L2 would be
the equivalent resistance seen on the primary of the transformer (600 ohm).
Does this resistance value works well to reduce the voltage across ring and tip lines so that
telephone will automatically turns into off-hook sate ?
2. Where can I fed-back some audio beeps to hear on the caller end after off-hook, on primary or on secondary
or on directly to L1 ?
I don't want to use separate Telephone Line Interface Modules (DAA's).
It has the property of blocking DC current through windings.
On detecting first ring voltage, BC547 will turn on line-relay to close line L2.
I have the following 2 doubts,
1. On turning on the line-relay, the resistance between the two lines L1 & L2 would be
the equivalent resistance seen on the primary of the transformer (600 ohm).
Does this resistance value works well to reduce the voltage across ring and tip lines so that
telephone will automatically turns into off-hook sate ?
2. Where can I fed-back some audio beeps to hear on the caller end after off-hook, on primary or on secondary
or on directly to L1 ?
I don't want to use separate Telephone Line Interface Modules (DAA's).
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