Select your language

Sometimes it is useful to record your phone conversation on tape. Feeding the signal directly to the input of the tape recorder or through the condenser with TL impossible. This is because if the tube lies on the unit, in line applies a constant voltage of 60 V, which is quite enough to damage the input stages of the amplifier. Will not save the schema of the tape used in the circuit coupling capacitor - because in the time of the call in the line can act AC signal with an amplitude of up to 200 V, and the input of the tape recorder, for the convenience of its use, should be permanently connected to the TL .

The design of the adapter

The illustrated design of the adapter allows you to use any recording tape having an input for connection external microphone. The device does not require power and can be permanently incorporated into the gap of one of the wires of the line going to phone the handset. (This does not degrade the quality of communication and eliminates damage to the input circuits of the recorder.)

The transformer provides isolation between the DC circuits. The inclusion of diodes VD1 and VD2 restrict prevents the probability of occurrence in the secondary circuit of the transformer of the AC voltage that is dangerous to the input circuits of the recorder level. And the level of the signal line is set by resistor R1 (its value may differ significantly from that specified in the scheme).

For the manufacture of the transformer T1 is used for the magnetic core from any telephone transformer (they are all unified, and his it is easy to find). It has a design that eliminates the magnetization of the magnetic circuit when the flow of direct current (when the handset from the handset withdrawn). Transformer dismantle and remove the upper winding frame. In its place is wound 120...140 turns of wire PEL-2 with a diameter of 0.33 mm. The remaining windings are included, as shown in the diagram, allowing you to raise the voltage in the secondary circuit.

With proper installation, the adapter does not require any adjustment.

Publication: www.cxem.net