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I have been looking at a diagram with this symbol on it. Does this symbol mean a relay or something else? The full wiring diagram is in the second picture for context.

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  • \$\begingroup\$ Looks like it could be an old symbol for a normally-closed relay? It's not at all the symbol used for those today, though. \$\endgroup\$
    – Hearth
    Commented Oct 18, 2023 at 12:21
  • \$\begingroup\$ That would make sense, given it's placement in the schematic. It's used to interrupt the red A path when the kickdown switch is closed. \$\endgroup\$
    – SteveSh
    Commented Oct 18, 2023 at 12:30
  • \$\begingroup\$ Is this for an automotive transmission? \$\endgroup\$
    – SteveSh
    Commented Oct 18, 2023 at 12:31
  • \$\begingroup\$ @Hearth ah yes i forgot to say this is from late 1960s \$\endgroup\$ Commented Oct 18, 2023 at 13:28
  • \$\begingroup\$ @SteveSh Its from the transmission of leopard-1 tank , i still couldnt figure out how exactly the kickdown works in this but, the "generator" things are 2 generators one for engine speed other for vehicle speed. and those generate voltage i think according to engine and vehicle speed which are then fed into that transistor area and in there the "automatization" of the shifts is done. light blue line goes to 1st gear, when that switch is interrupted and if relay or wtv it is bridges the gap to yellow wire then 2nd gear will engage and so on. (i think) \$\endgroup\$ Commented Oct 18, 2023 at 13:30

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This appears to be an unusual symbol for an unusual type of relay. The full symbol is more than what you've shown: those two circles to the right are also part of it.

enter image description here

It would appear that, when the relay is actuated by a signal to the base of that transistor, the coil (box with a slash through it) causes the contact (thick black bar connected to the coil with a thinner bar) to move from bridging the left terminals (unfilled circles) to bridging the right circles.

This is not how most relays work. Most (double-throw) relays have three output terminals per pole: a "common" contact that is always connected, and two other contacts that are connected or disconnected to common depending on the state of the coil. This one seems to function differently; it may be a contactor.

Contactors (which are a special type of relay, usually rated for very high currents and frequently with additional features like a second pair of low-current contacts for feedback) typically do use such a bridging structure (which increases reliability by having two points where the circuit is broken instead of just one), but it's uncommon to see double-throw contactors; usually they only have one pair of output terminals that are either connected or disconnected.

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  • \$\begingroup\$ i see thank you! also i heard transistors can be "partially on" and that they can let some current pass through but not all until they are fully energized and then they can let all the current through when they are fully energized. if that is true, in this case if lets say transistor was partially on and let some current thru but not all, would that thing i asked about also be partially on i.e. would it move towards the right a bit but not fully? or would it not care about it at all and only fully go right when transistor fully energizes? (by the way i dont know much about electronics) \$\endgroup\$ Commented Oct 18, 2023 at 13:35
  • \$\begingroup\$ @TimothyScherer This is not a mode of operation that's designed to be used, so even if you can it wouldn't be stable or reliable to hold it in that state. You'd have to be very careful about how much current flows in the coil. \$\endgroup\$
    – Hearth
    Commented Oct 18, 2023 at 13:40
  • \$\begingroup\$ i see thank you. I wondered because this transmission is supposed to shift slower in auto mode compared to when shifted manually with those 1-2-3-4 positions as you can see in the gear lever. According to a Leopard-1 driver that i know, the transmission will actually shift out of gear , stay in neutral for a little bit of time and then engage the new gear hence why its slower. If that thing i asked stayed in like mid way thru somehow in that case it should be in neutral for a little bit of time until the upcoming gear engages so thats why i was wondering if that would be possible. \$\endgroup\$ Commented Oct 18, 2023 at 13:47

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