Hello.
I assume that TA-10/TA-20 are not simply battery charger, and at the same time serves as an antenna-feeder path. Since to all previous GTM-xx models in addition there was "Antenna Extension Cable with Suction Cups (Part Number: 010-11282-00) " Now for it there is no connector (mini-jack) in the navigator. I think that its function is executed now by TA-10/TA-20