Courtesy of Eric W2ZT:

The internal SQ line of the G707A presents an active low with an open squelch in carrier mode (received signal). When in CT mode, its an active low only when the proper PL frequency is received. Accordingly, I modified my TM-G707A by routing the internal SQ line to pin 6 on the radios mini din socket (replacing the current connection). My method of doing this required the cutting of a circuit trace on the Control board (current din connection) and routing a wire from pin 11 of CN502 to the din socket pin 6.
 
This SQ line can be found at CN4 pin 11 on the main TX-RX board or CN502 pin 11 on the Control board (behind the front panel). If you dont wish to perform this modification to the din socket (kind of intricate), you can simply attach a wire to one of these points, then route it out of the radio and connect it to the DB9 (pin seven) of your chosen controller port.
 
This will facilitate fully agile CTCSS decode &/or encode functionality using only the A72xx1 or A72xx2 commands without the need for an external PL decoder. Additionally, the remote base controller port can be left in carrier mode. Dont forget to change the jumper plugs on the controllers remote base port from active high to active-low.
 
Hope this helps someone.
 