My TV has two SCART sockets, to which 4 devices are connected as follows: 1. Sky>TiVo> SCART SWITCHER > TV DVD Player > Sky can only be viewed when TiVo is switched on. 2. VCR > TV The sound of the Sky box can be heard through the TV when the SCART switcher is switched to TiVo and TiVo is off, and also when the switcher is switched to the DVD player and it is turned off. What might be causing this?