I have to make a box which has 2 data input and 1 data output and a power input. Data Input: 1. a connector with 3 wires valid, they are a pair of differential signal and a reference level (common) 2. a connector with 5 wires valid, they are a pair of differential signal and AC source (L, N, E) Normally, there should be only 1 data input port being used, either the 3 wires or 5 wires 1, but not both. When the 3 wires port is used, then the box should forward the 3 wires port's differential signal to the data output port. When the 5 wires port is used, then the box should forward the 5 wires port's differential signal to the data output port. But in case if user didn't use it correctly, and plug in wires on both data input ports, then the box would have a rule (it not yet set, maybe can set it after I got the circuit) to detect it and forward either 1 of the data ports' differential signal according to the rule to the data output port. I'm thinking of using a switch IC (2 input and 1 output), connect the data input ports' differential signals to its input pins and connect the data output ports to its output pins. For the control pin, I think of using 2 diodes connect to either 1 of the input ports' differential signals, but the input signal can be up to 1MHz, will it have any abnormal at the control pin during its rise or falling edge? http://totao.homelinux.com/phpbb/download/file.php?id=3912 [Broken] On the other hand, I'm also thinking a about the same way, but use the L and N to detect for the port, use a relay with ac input at coil side, and use the switch side for the control pin. But I tried to search some vendor, there's not many ac control relay, even yes, its voltage range can't cover from 90V ~ 260V (I only can find something about 110V). Any comment can give me? Any opinion on any method to reach my goal is welcomed.