Slide switch (SPDT)
A three-pin SPDT slide switch: the pole in the middle moves between the two ends as you click it.
2 is the common pole; the slider ties it to 1 or to 3 and to nothing else. The
pole that is not selected is genuinely open: high impedance from both sides, so a
net hanging off it floats exactly as it would on a real breadboard.
Pins
| Pin | What it does |
|---|---|
1 |
One throw. |
2 |
The common pole. |
3 |
The other throw. |
Properties
None.
While it runs
Click the switch on the canvas to move it between its two positions while the simulation runs.
What the model gets right
No pin is treated as an "input": a slide switch passes whatever is on one side through to the other, in either direction, which is what makes it just as useful as a supply selector as it is as a logic-level input.
What it does not model
No contact bounce. A real slide switch chatters for a millisecond or so on the way across, but nothing in the firmware library needs it modeled, and a silent approximation beats a wrong one. The pushbutton is where bounce is modeled, because a debounce lesson actually needs it there. Nor is there any travel time: the pole leaves one throw and arrives at the other in the same instant, where a real slider is genuinely open for a moment in between. There is no contact resistance drift, no wear and no current rating.
Common mistakes
Expecting the unselected throw to read as a defined 0 or 1 rather than Floating. With nothing connecting it to either the pole or a pull resistor, it really is undriven.
See it in action
555 blinker uses a slide switch to swap the timing resistor while it runs; NAND latch and Full adder both use one as a logic-level input selector. See them at /templates.