Thanks for your response, which, I'm very pleased to say has a good understanding of my scenario. Actually I had connected up a BT Youview box and was just coming on here to post my findings. The RF passthrough does indeed work, and very well indeed. One of the best, in terms of quality, which I have seen. It seems to have an anitference filter yet no loss in strength. Very impressive, as this box is, as a whole. It's excellent. Just to respond to your comments, as you have taken the time to reply to me in depth which I appreciate. The CCTV signal is modulated into an RF frequency, which is then distributed and fed into the digital antenna cable and then reaches several TV sets including the Youview box. The digital TV signal is then sent to the TV via HDMI in the normal way, and the modulated RF signal then passes through the box, again (in this instance), to the same TV using a standard RF patch cable. You are correct in that by changing the TV input selection, one can switch between Freeview and the CCTV and back again. Although a little cumbersome, but what I expected, which is what prompted my question of switching methods between the two. Now, the previous Thomson freeview box which was connected (and connected in the same way, albeit scart in place of HDMI), had a rather quaint button on the remote, which, in just one process turned off the digital signal leaving the only available output being the RF passthrough (note passthrough only, not an actual RF frequency as although this box did have that feature also, it was user disabled), therefore the CCTV image displayed on the TV, as the TV recognised this as the only live input. It's a unique feature I feel with the Thomson box, and a couple of others also. The same result can be achieved by turning the digi box to standby, and, as mentioned by us both, using the TV remote to change inputs, both of those methods being more clumsy obviously. Thanks again for the replies, appreciated!