Any idea what this oddball vintage plug is? Three-conductor, 1/4" size.

[EastPoint]

I picked up this vintage cable the other day. It has a plug on one end that's similar in size to a 1/4" plug, but has three conductors instead of two. Any idea what it's called and what it's for?

 

[restorer-john]

I'm pretty sure some old-skool dictation/transcriber machines used plugs like that for the headset/foot pedal. Or maybe a aviation/military locking headset plug?

 

[merlynski]

Looks like an old telecom 310 plug for telephone Central Office patching: Tip, Ring and Sleeve connections.

 

[restorer-john]

Looks like an old telecom 310 plug for telephone Central Office patching: Tip, Ring and Sleeve connections.

Winner winner!

 

[wlgrant6]

Looks like an old telecom 310 plug for telephone Central Office patching: Tip, Ring and Sleeve connections.

Been there, done that. Bill

 

[Catmanboo]

I concur, telecom plug common to central office & other duty. Also, mil-spec for similar use. Will likely work as headphone plug if it's 1/4".

 

[merlynski]

Further info to help answer question: http://www.tech-faq.com/tip-ring.html

 

[Ray Gianelli]

You guys are correct. 310 cable, used in Central Office for access or monitoring of T1 circuits.

I should know; I'm sitting in a telco central office as I type this... but not a single 310 panel to be found! They were replaced by bantam and 800 style panels.

 

[KingBubba]

I have seen thousands of those in my working days. That type of plug is very common in audio patch cords as well as old telephone patch cords. They were also used to direct lighting console systems to the individual dimmer packs in the late 70s and early 80s. Stagehands were actually given cues by the stage manager to change the patch cords from the light board for different lighting scenes. I can remember standing backstage and having to do that on cue.