Fishman ACC-AG1-4PN 4 pin TRSS Switching Stereo Endpin Jack, made by Switchcraft. Standard 1/4" female instrument jack, can be wired in mono or stereo. Has extra contact to turn battery on (for a preamp) when cable is plugged in, off when cable is removed.
Refer to the wiring diagram on the Fishman website for wiring instructions.