Compatible to Motorola M(1) style 2 pin connector, although that connector using mono jacks.

3.5mm jack

	Signal
Tip	SPK- (Vcm = 2.5V)
Ring	internal 10K PU to 3V3, unknown purpose Short circuited to sleeve when using the SSM-17B Hand speaker Mic. Maybe that's the reason why Yaesu doesn't market the SSM-17B as an accessory to the FT-65. The SSM-512B is advised instead.
Sleeve	SPK+ (Vcm = 2.5V)

2.5mm jack

	Signal
Tip	MIC : 100nF to 10µF AC-coupling from tip to microphone element PTT : Put 2Kohm from tip to GND to enable PTT.
Ring	RX/TX Short circuited to sleeve when using the SSM-17B Hand speaker Mic. Use open drain TX and connect it to RX. Another option is to connect the anode of a diode to the RX-line. Connect the cathode of that same diode to the TX-line.
Sleeve	GND