Banana Jack Pinout
Single-conductor 4 mm spring connector used for test leads, bench supplies, and speaker terminals.
Overview
A banana jack is a single-pole connector: one jack accepts one banana plug carrying one conductor. The standard size uses a 4 mm diameter plug whose sprung sides grip the inside of the jack barrel.
Because each jack is one pole, a connection uses a pair - one positive/signal and one negative/return - typically color-coded red and black. Many instruments add a green jack for protective earth.
Pinout
| Pin | Name | Function | Description |
|---|---|---|---|
| 1 | Conductor | VIDEO | Single conductor (one pole); paired red (+) and black (-) jacks form a circuit |
Notes
- Single-pole - polarity is defined by jack color (red = +, black = -, green = earth).
- Standard plug diameter is 4 mm; a 2 mm 'mini banana' variant does not mate with 4 mm.
Reference: Pomona Electronics - 4 mm Banana Plug & Jack catalog· verified 2026-06-27