Quick Answer:The One Way Plug Key is a single-pole, single-throw plug switch: two brass blocks separated by one gap, closed by a tapered brass plug with an insulated head to give a low-resistance on/off contact in a circuit branch.
Last updated: 18 October 2026
Key Features
Single-pole single-throw (SPST) plug switch.
Two heavy-duty brass blocks with one gap.
Tapered brass plug with insulated moulded head.
Two terminals for connection.
Technical Specifications
Specification
Value
Switch type
SPST plug switch
Blocks
Two, high-conductivity brass
Gap
One
Plug
Precision-ground tapered brass, insulated head
Terminals
Two
How It Is Used
The key is placed in series in the branch to be controlled. Pushing the plug firmly into the gap closes the circuit with very little contact resistance, and pulling it out opens it, which suits sensitive galvanometer, bridge and potentiometer circuits.
Frequently Asked Questions
How does the One Way Plug Key switch a circuit?
Inserting the tapered brass plug between its two brass blocks closes the circuit; removing it opens the circuit.
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