Hi,
> I believe my 'voice line' is being tapped [the line feeds through the
> 'opponents' switchboard].
> How difficult is it for them to 'decode' my modem [to ISP] traffic ?
> I'm guessing/hoping that my modem has to 'synchronise' with the ISP's
> in analog mode, so it's difficult for a '3rd' party to listen ?
I'm not sure about current modems. With early modem technology (1200 baud and below), eavesdropping was easy.