Here is the top of the handheld.
I think its 26 female pins.
Then there is a phone plug with a single female plug below it (power?) on the left side , and a phone plug on the right side.
It takes a master cartridge or an auxillary cartridge.
Here is a pic of the top, above the screen:
This unit originally came with a MARINE cord and cartridge ... I wonder if it was custom swapped out with a different piece up top to connect the cord to?
Thanks for pointing out I have a Tech 1 power/data cord ... I didn't even realize it was different than a tech 1a , that helps me a lot ! ---