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I have a multi-pin connector that I would like to be able to turn off with a single switch. How would I do that?

The situation is that there is a multi-pin connector cable (like an RS-232 connector) with two outputs. So, the cable will fork. One connector is permanently connected to a monitoring system which is always on. The other connector is free-standing and is only used for occasional test purposes.

When the test connector is used, the monitoring connector has to be turned off because otherwise it will send commands and electrical signals down the cable constantly. So, basically I need to switchover the cable from the monitoring device to the test connector.

Now, of course I could install a small switch on every wire in the cable, but it seems silly to install 24 switches or whatever. Is there a way to make all the wires go one way or the other using just one switch?

Note that it does not need to be either/or, I just need to turn off the connection to the monitoring system when required. I cannot do this by unplugging it because the monitor is installed in a panel that takes over two hours to disassemble, so unplugging it is not a good solution.

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  • \$\begingroup\$ You need a multichannel (electronic) switch. One way it to use a ready made IC that will need some commands (e.g. via SPI) to bank from one side to the other. You need to find one with appropriate number of channels for your app. You could also build something rather simple with discrete components, but will take more board space. Maybe someone will add a schematic for that (ain't complicated). If you want that, you should probably add what kind of logic (and/or voltages) your bus is using. \$\endgroup\$ – Fizz Oct 6 '15 at 0:25
  • \$\begingroup\$ Hmm, "multichannel switch", interesting, does it operate parasitically off the signal voltage or does it require an independent power source? \$\endgroup\$ – Tyler Durden Oct 6 '15 at 0:44
  • \$\begingroup\$ Needs own power. I don't know if your bus supplies power too. To give you an example of what's involved, you could use a bunch of 74VHC4053; each of these is a triple 2-channel analog multiplexer; these are CMOS-level commanded. In your application you basically have a 1-bit address (and a number [24?] of [analog?] data lines). \$\endgroup\$ – Fizz Oct 6 '15 at 1:06
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Now, of course I could install a small switch on every wire in the cable, but it seems silly to install 24 switches or whatever. Is there a way to make all the wires go one way or the other using just one switch?

Yes, but rather than involving active electronics, you can just use a 24-pole switch. Such large switches were once fairly common computer accessories, used to select one of multiple peripherals to be used with a port that could only use one at a time. They were known as “data switches”, and they had a common look despite being made for a wide variety of interface types:

(Google Image Search result examples)

I'm not certain that all such switches with 25-pin connectors would actually have 25 separate lines, but I think it's worth taking a look (and a continuity tester or a screwdriver) around the nearest surplus electronics shop, rather than necessarily building a similar device from scratch. You could either build an adapter from your connector to DB-25, or open it up and replace the connectors.

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