corey

I Have searched throughout this site and haven't found a close solution to this, although I know it is probably simple. I have a customer with a gate and a call box. When someone pulls up to the gate, he wants the televisions in the house to go the the camera inside the call box. My question is: What device can I use to switch the signal from cable to cctv when motion is detected at the call box? I have thought about actually rewiring an A/B switch and a time delay relay. Thank you.