PIN	Function	Direction	Notes and limitations
1	CTCSS logic output (active low)	Out
2	Receive audio input - to band pass filter	In	Operates only in RX mode
3	Discriminator audio input	In	Connects also to pin 16
4	CTCSS tone output	Out	Operates only in TX mode
5	Receive audio output - from BPF filter	Out	Operates only in RX mode
6	CTRL (control) Input	In	Must be grounded for decode mode.
7	Spare - can be routed anywhere desired	In/Out	Can connect to A - B outputs or elsewhere
8	Spare - can be routed anywhere desired	In/Out	Can connect to A - B outputs or elsewhere
9	RX - TX mode switch	In	Ground for TX mode (encode only)
10	CTCSS logic output (active high)	Out	Current limited - includes a pull-down
11	Spare - can be routed anywhere desired	In/Out	Can connect to A - B outputs or elsewhere
12	Spare - can be routed anywhere desired	In/Out	Can connect to A - B outputs or elsewhere
13	Power supply positive (+7 to +16 VDC)	In	7 - 16 VDC typical, up to 24 VDC maximum
14	PTL (push to listen)	In	See Seiko S-7119 data sheet for operation
15	Spare - can be routed anywhere desired	In/Out	Can connect to A - B outputs or elsewhere
16	Discriminator audio in/output	In/Out	Connects to pin 3
17	N/C
18	Ground
19	Ground
20	Ground
21	Ground
22	Ground
23	Ground
24	Spare - can be routed anywhere desired	In/Out	Can connect to A - B outputs or elsewhere
25	Spare - can be routed anywhere desired	In/Out	Can connect to A - B outputs or elsewhere
NOTE:	Use outputs A - B only when primary logic outputs above cannot be used!	NOTE:	These can be tied to "Spare" pins 7, 11, 12, 15, 24, and 25.
A	Alternate Open Collector CTCSS output (active high)	Out
B	Alternate Open Collector CTCSS output (active low)	Out