Hi Ijaz,

Don't mention it :o)

TDR is Time Domain Reflectometry. It works by sending a very short, very steep pulse down a transmission line and analysing the reflected signal. This makes it possible to detect impedance anomalies.

Agilent (formerly Hewlett Packard) have an application note on the theory of TDR. And if you really want to know about bugging, wiretapping, etc. then you should visit www.tscm.com

Regards,
Rob.