600Ω/600Ω isolation transformer

[vinodquilon]

How can I design and setup 600 ohm to 600 ohm modem transformer ? Pls give me details about no.of turns, core type, coil type, etc. Is concentric type winding is enough. The aim of the transformer is to tap telephone line.
In our local market it is not readily avail...

 

[audioguru]

Find an old dial-up modem that is not used anymore and steal its transformer.
Or take one from an old telephone answrering machine.
Or from an old speaker-phone?

 

[dougy83]

You can just use a couple of capacitors to tap audio from a telephone line.

 

[audioguru]

You can just use a couple of capacitors to tap audio from a telephone line.

You need perfect isolation that is provided by optical or a transformer.

 

[mneary]

A 600 ohm transformer attached to a telephone line is not a tap. It would be more like a terminal device.

 

[Externet]

A plain audio output transformer 8Ω to whatever, NOT 600:600, can be connected with the 8Ω winding in series to only one telco wire to inject/pick audio. Precautions for protecting the circuit from damage due to the ring signal have to be taken.
RadioShack sells one.