Simple Phone Tap

This circuit is extremely simple, therefore there is less chance of any problems. It can be placed anywhere on the phone line and it will record any conversation on any phone on that line.Please note: I have received several emails saying that this circuit will not work and that it may hold your line off hook and to me it looks like it will (it would put quite a load on the phone line). For some, it has worked fine. Build at your own risk.

Schematic

Parts

Part Total Qty. Description Substitutions R1 1 470 Ohm 1/4 Watt Resistor R2 1 1K 1/4 Watt Resistor R3 1 100K 1/4 Watt Resistor R4 1 6K 1/4 Watt Resistor C1, C2 2 0.01 uF 100V Ceramic Capacitor K1 1 24VDC Reed Relay MISC 1 Wire, Headphone Plugs, Phone Plug Or Alligator Clips

Notes

1. Email Derek Tombrello with comments, questions, etc.
2. To use the circuit, simply connect it in series to the phone. Then plug in the recorder. It will start recording when the phone is picked up.
3. The values of R1 and R2 may have to be adjusted, depending on the characteristics of the phone line it is connected to (they vary). If the R1+R2 combination is increased sufficiently (try 2.47K) then the circuit can be connected in parallel with the line, thus covering all attached devices. (Thanks to Mark Wright for the suggestion).
4. T.A. Betts offers this suggestion for getting this problematic circuit working: "If you drop the resistors and add a 2.2uF capacitor the line will not stay off hook. It blocks the DC from the moniter position."