what is Characteristic Cable Impedance ?

Characteristic cable impedance (Zo) is a very important measurement in determining a cable's transmission capability. Maximum power is transmitted when the source has the same impedance as the load. Therefore the cable (line) should have the same characteristic impedance as the transmission equipment. The Zo of the transmitting equipment drives the maximum signal into the line and in turn the Zo of receiving equipment determines the maximum signal out of the line. Ideally, ZoTRANSMITTER = ZoLINE = ZoRECEIVER. When the characteristic impedances do not match, part of the signal is reflected back to the source degrading the transmission path.