isolation transformer costs $45!!!!!!!!!!!

I am planning to tap a telephone line through an isolation transformer 600Ω/600Ω of 1:1 type. In our local market it is not readily avail. After a lot of search I have found one Dax 56K DX-56PU modem from one electronic shop and they put forward $45 for modem. Actually I only want one small transformer inside it.

Find the attachment. Non-SMD Type transformer with white colored core. T1 AASUPREME.
I have heard there also exists modem line transformers with 600Ω primary and different secondary (600,330,560,etc) resistances. How can I fix this should be 600Ω/600Ω Type.

Does it is mandatory to use 600Ω/600Ω in Telephone tap......

Can I possible to take outs from transformer leads on underside of the PCB without desoldering the costly PCB board.

Yes, you need an isolation transformer to comply with the safety regulations.

My local supplier sells 600R transformers, they start as £2.95 which is $4.61 (US).

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If you are tapping a telephone line, the impedance has an effect on voice quality. But you should get good results if the transformer is any impedance between 600 and 2000 ohms. A ratio anywhere from 1:1 to 3:1 should work in most circuits.

WARNING: This assumes that you are not running any DC through the transformer.

The DC can be removed by connecting a capacitor in series with the transformer's primary winding, 1µF will be enough to pass all frequencies down to 300Hz which is the lower cut-off for a phone line. This assumes that the transformer is connected to a 600R resistive load, otherwise the capacitance can resonate with the winding inductance.

Salvaging one from a discarded modem, isn't an option?

Or an ethernet based device? I don't know if they're suitable for telephone work but all Ethernet devices require isolation transformers.

I think they still use dial-up modems in India. They are about 20 years behind us. Many people there don't have electricity unless they connect to it themselves and steal it.