Tevion twin screen portable dvd player TWS704.Connection for AV socket?

I have brought this from Ebay and is working well except for the AV socket, yellow one on the side by the headphone socket. The cable that came with it has the same plug that fits the monitor with red, white and yellow phono plugs for the tv on the other end. When I connect from the player to the tv there is no picture and a humming sound. The manual seems to suggest that the video comes from this socket and the sound from the earphone socket. Can anyone help as to what the connection type should be.