PC-to-transceiver audio interface

Sometimes there are quick and easy construction projects on my long 'to do' list, e.g., a pc sound-system to transceiver interface. I have one already, ( just visible in the picture posted on 14th July 2012 ); but with the arrival in the shack of pc number 5 another interface would be convenient. The existing one incorporates transceiver mic switching, mic gain and speaker. The one I have just completed is basic, containing only the bare essentials of the two line isolation transformers.
The transformers provide the path for audio without allowing any dc connection which is the preferable situation when connecting together these two valuable pieces of equipment; radio transceiver and computer.
I obtain these transformers from discarded telephones and modem cards. Using temporary connections, the windings and taps which give the best results on both transmit and receive can be identified. In the finished interface the transformers are orientated for minimum interaction.
Currently I have two spare transformers, sufficient for another interface; one from a telephone, and the other yet to be removed from a modem.