sundance-communications.com Forums Telephone Services Telephone Repairs & Equipment Music on telephone

I am possibly going to do a telephone museum, now that I have some interesting phones from different generations.

I want people to be able to pick up the phone, and hear music from that generation of the phone models introduction.

How can I wire up an audio output from say, an iPod, into the phones line cord? Obviously mono, but can I just wire the output to the green and red wires on the line cord?

Yes, but you'll probably need more level than an iPod. I'd suggest having a 1 Watt output available. And for best sound, 600 ohm impedance. And don't waste time with high fidelity. Telephone audio is limited to 300-3300 Hertz, for reasons that we needn't go into. Oh, you might want to remove the transmitter, as well.

I know not to go HiFi.

I'll get a multi channel amp which can surely output that and impedance, and unscrew the Mic..

Thanks..

Actually, 600 ohm impedance is kinda few and far between. You may have to use resistors to create a 600 ohm impedance. Which means you'll lose power. Radio Shack used to sell an 8 to 1000 ohm center-tapped transistor output transformer. Center tap to one end of winding is 500 which is close enough. Now if only they still sell it or someone has a few.

Couldn't I just try and find a potentiometer that has it in it's range? That should be far easier than a resistor alone..

Heck, see how it sounds mismatched, if it's ok, ok. Otherwise, put a 300 ohm resistor on the green wire and another on the red wire. Anything from 250 to 350 will be fine and I don't remember what the standard 10% resistor is in that range. The idea is the phone will see a total impedance of approximately 600 ohms. 300+ 8 (the amp impedance)+300 = 608.

John, what do you mean by 10% resistor? How many watts is it? I'm looking at my Newark catalog.

Standard resistors are made with a tolerance of either 5% or 10%. For serious money, you can get 1% or less. 1/2 watt would be entirely satisfactory. 1/4 watt will also be fine and probably easier to find these days. Remember, the phone will also have about 600 ohms of impedance, when you start doing the calculations and it looks like the resistor should go up in smoke instantly if not sooner. So the power is actually dissapated across 1200+ ohms.