Wie weet wat dit is? (Toestel of techniek)

door Oldtimer , Oegstgeest, 18-03-2020, 22:07 (1497 dagen geleden) @ Leo Snoeren

Zie:
https://www.epanorama.net/circuits/teleinterface.html

Philips recording interface

The first circuit is Philips LFH0117/00 telephone recording adapter, which is not manufactured anymore I think. The circuit is quite typical telephone recording adapter design. I have used succesfully for getting audio from telephone line to soundcard and my stereo system.

The circuit is designed to be connected in parallel with normal telephone. This circuit does not provide any DC path or correct impedance matching to telephone line because the telephone provides them (this circuit is designed so that it disturbs the operation of telephone as little as possible so it has high impedance input).

Philips adapter circuit

I found out the type of all other components than the transformer T1. T1 is the audio isolation transformer, which seems to have properties quite similar to typical 600:600 ohm telecom isolation transformer. The components F1 and F2 are 50mA fuses. The signal output level is suitable for microphone input because the resistors attenuate the voice signals form telephone line around 40 dB (some telephone equipment regulations in Finland needed this). On the picture below you can see a picture of the inside of the Philips LFH0117/00 telephone recording adapter:

Willem