I'd like to have some kind of electronically controlled switch (transistor, relay, solid-state relay, etc) that acts as a break in a RS-485 bus. The effect I would like is to optionally split the bus into two halves, isolating one half from the other. Obviously RS-485 signals would need to be transmitted clearly (even high-speed 2Mbps+ signals) when the switch is in the 'on' state and no signal should get through when the signal is in the 'off' state.
What kind of component should I be using, and how should I wire it up?
P.S. I'm looking for a component that is as physically small as possible, and I'd like the switching voltage to be 5V or lower.
P.P.S. The RS-485 bus cables in my application will be short enough that signal reflection won't be a problem, so I'm not going to worry about any termination at the moment. Nevertheless, bonus kudos is available for a solution that could optionally incorporate switching in a termination resistor on each side of the break – as I'm sure that would be useful to someone in the future.
Best Answer
You can just use a relay, optionally switching over to a couple of termination resistors each side.
Edit following WRB's comment: If the system can't stand a bit of junk on the bus (which would seem like an oversight in something relying on RS485) then look at quiet relays (mercury wetted for example) or perhaps putting two RS485 transceiver IC's back to back.