> DC blocking capacitor Richard/John, thanks So - Series DC-blocking cap (I see values 0.47u - 1u used) with a relay pole to short that on connection, the impedance of the Tx signalling off-hook to the exchange -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist