Sony KV19 Scart - AV Ext switch

I have recently bought a Philex AV transmitter and am trying to transmit from a Sky+ box to a KV19.The KV19 gives me 29 channels and has a scart socket but nothing seems to happen when I plug the Philex receiver onto the Scart socket. Is there some way of switching the Scart on - there does not seem to be an EXT or an AV channel?! Thanks.