I'm using the attached circuit as a phone dialer and audio message deliverer. I have two issues that I need help with:
01. When I use the circuit from my PC that has an amplified audio port it works fine. When I use it from my Raspberry Pi the volume is not loud enough, even at max, for it to dial. So, I need to build in an amplifier of some sort. I'm thinking of using an LM380 but I'm not sure which side of the circuit I should use it?
A. On the PC audio out before the transformer?
B. On the PC audio out after the transformer?
C. On the phone line section after C1 and R1?
D. Other?
02. I would like to protect this circuit from accidental rings coming from the outside world. It is connected to an analog phone line that is not supposed to ring but it can if someone dials the number.
FYI - R1 is a 470 ohm resistor that makes the circuit trigger an off-hook state. It has a relay to control it that I have not included in the schematic.
Any other advice or suggestions would be greatly appreciated. Thanks.
01. When I use the circuit from my PC that has an amplified audio port it works fine. When I use it from my Raspberry Pi the volume is not loud enough, even at max, for it to dial. So, I need to build in an amplifier of some sort. I'm thinking of using an LM380 but I'm not sure which side of the circuit I should use it?
A. On the PC audio out before the transformer?
B. On the PC audio out after the transformer?
C. On the phone line section after C1 and R1?
D. Other?
02. I would like to protect this circuit from accidental rings coming from the outside world. It is connected to an analog phone line that is not supposed to ring but it can if someone dials the number.
FYI - R1 is a 470 ohm resistor that makes the circuit trigger an off-hook state. It has a relay to control it that I have not included in the schematic.
Any other advice or suggestions would be greatly appreciated. Thanks.
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