600Ω/600Ω isolation transformer

vinodquilon

Member

• Jan 25, 2010

• #1

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

Well-Known Member

Most Helpful Member

• Jan 25, 2010

• #2

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?

 

D

dougy83

Well-Known Member

Most Helpful Member

• Jan 25, 2010

• #3

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

 

audioguru

Well-Known Member

Most Helpful Member

• Jan 25, 2010

• #4

dougy83 said:

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

Click to expand...

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

 

M

mneary

New Member

• Jan 25, 2010

• #5

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

 

Externet

Well-Known Member

• Jan 25, 2010

• #6

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.