Echo cancelling for enhanced PAL

Echoes can occur in any communication system where more than one signal path is available between the transmitter and the receiver. In television such echoes are usually called ghosts, because the effect on the received picture is to produce faint repeat images of the main picture. In the light of plans for European broadcasters to introduce wide screen television services based on enhancements to the existing PAL system, consideration should be given to the effect of echoes on such enhanced systems and techniques which can be used to reduce these effects