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I suspect this switch isn’t functioning correctly and would like to replace it but can’t find one similar. What sort of switch is it?

The front is a push with two states (in/out) and has a bulb to indicate on/off (though that’s not currently working). It’s probably from early 90s or late 80s.

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This is a similar switch that I got a better photo of, though it has extra wires out. The switch of interest is in the background.

enter image description here

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  • \$\begingroup\$ The [RS] logo is the central hint here: rs-online.com \$\endgroup\$ – Marcus Müller Mar 13 at 15:58
  • \$\begingroup\$ @MarcusMüller yup, no part number though. I have had a look at rs-online but couldn’t see a match, hoping someone else with more knowledge of what they’re searching for may have more luck. \$\endgroup\$ – Notts90 Mar 13 at 16:00
  • \$\begingroup\$ I have found similar looking ones such as this but there are several that look identical that have different descriptions. \$\endgroup\$ – Notts90 Mar 13 at 16:13
  • \$\begingroup\$ It looks like it may be energizing a relay through the bulb. I could see doing that if it were essential to safety to only energize a circuit when the bulb was lit -- running a relay coil through the bulb would insure that a burnt-out bulb de-energized the relay. If that's the case, then replace the bulb and you'll be back in business. \$\endgroup\$ – TimWescott Mar 13 at 16:20
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The diagram on the side is pretty clear -- the top terminals are for a bulb, the "middle" (one up from the bottom) terminals are a NC contact, and the bottom terminals are a NO contact. It's almost, but not quite, a SPDT switch -- it's more like a DPDT switch that's missing some terminals.

BUT looking at the picture, it's running current from the contacts through the bulb. It may be that the burnt-out bulb is an essential part of the circuit (possibly for safety reasons, to never energize a circuit unless there's an indicator light).

Dig through the rs-online site; this should be pretty obvious.

If all you need is a replacement, and looks don't matter, then by the diagram and the wiring, only the NC section (and possibly the bulb) is being used -- so you just need a normally-closed (or closed-when-out) SPST push-push switch with a bulb.

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It’s either a momentary or toggle push-push latching switch . What makes you think it is not Functional?

They do make cheaper ones too. https://uk.rs-online.com/web/p/push-button-switches/0319449/

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  • \$\begingroup\$ It’s latching rather than momentary. The continuity didn’t seem right, might be because we didn’t realise the type of switch. \$\endgroup\$ – Notts90 Mar 13 at 17:36
  • \$\begingroup\$ How does it feel? \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Mar 13 at 18:05

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