I don't have the schematics to the 241 in front of me, but if it works the way I think it does, the PTT line is pulled to vcc, and needs to be pulled down to a 1K7 load (1.7K). Look at my page you bookmarked, at the end. You see the diode (reverse voltage protection) and the resistor to ground (bleed off) to the gate of the MOSFET (cheap - 50 cents or so with mouser.com). Put the 1.7K resistor in series between the source of the MOSFET and the PTT line. On signal activation, the positive voltage on the gate causes the MOSFET to conduct, and the source of the MOSFET goes to near 0 VDC.