2 Pin Serial (non-standard) connectors using the speaker/mic in/out are used in many two way radio brands including Kenwood, Baofeng, FDC, Linton, Pofung, Puxing, Surecom, Weierwei, Wouxun, and Quansheng.
Basically the cables that use these connectors use a chipset to convert sound to serial data, much like a modem. The data can then be processed and used to program the connect device via software like Chirp.
