The Manfrotto 522SCA is an available option for the 322RS electronic shutter release for the 322RC2 grip action ball head, and also a replacement remote control for the 521, 522, & 523 remote controllers. It is a standard coiled subminiphone male (2.5mm) to subminiphone male cable, 9.8" (25 cm) in length normally and expanding to 19.7" (50 cm) when uncoiled.
This is the 'stereo' version of the subminiphone cable; some 2.5mm devices don't need the 'stereo' function of the plug, but it would likely still function normally with them. There are quite a number of various products on the photographic market which employ this 2.5mm subminiphone connection.