Hi @haruki ,
Welcome to DigiKey TechForum and thanks for your inquiry.
The DIP switch MPN#204-121ST is a Single Pole Double Throw (SPDT) type, meaning it has:
- One common terminal (C)
- Two output terminals (typically labeled 1 and 2)
In the schematic diagram:
- Pin 1 and Pin 4 form one switch path
- Pin 2 and Pin 3 form the other switch path
Correct Interpretation of ON/OFF States
Your understanding is mostly correct, but let’s clarify it precisely:
When the switch is in the OFF (default) position:
- Pins 2 and 3 are connected
- Pins 1 and 4 are not connected
When the switch is in the ON (actuated) position:
- Pins 1 and 4 are connected
- Pins 2 and 3 are not connected
This behavior matches a locking SPDT switch, where the toggle or push action changes the connection from one path to the other.
Tip for Testing:
You can verify this with a multimeter in continuity mode:
Test between pins 2 and 3 when the switch is not pressed.
Test between pins 1 and 4 when the switch is pressed or locked ON.