AC adapter is Radio Shack part number 26-3804. It’s 6V DC at 400mA, with a 5.5mm outer diameter barrel plug, with the center “tip” conductor negative. The center pin on the jack was measured to be 2mm diameter. The CUI EPS060100-P5N appears to be a modern equivalent.
Fortunately, the computer is reverse-polarity protected, so I didn’t blow up my computer when I plugged in a more common tip-positive adapter. The path from the batteries to the computer is interrupted when a plug is inserted.
The Model 200 will not operate if the memory power switch (on the bottom of the computer) is set to “OFF”. If you’ve turned it on, and the computer still won’t respond, press the RESET button.
The modem is 300 baud, and exposes both an acoustic coupler and telephone line interface. The connector on the computer is a female 8-pin DIN, 262-degree style. The mating plug I bought numbers the pins differently, so take care cross-referencing against the Model 100 schematics. (TODO: Make a diagram)
If a red wire is soldered to to the ring pin (pin 3) and a green wire is soldered to tip pin (pin 7), you can connect those wires to the red and green wires on a telephone line and make calls!
The TELCOM program is a bit peculiar by modern standards. I recommend reading the documentation.
Set “STAT” to “M8N1ENN,O,T” to use tone dialing, as the Model 100 will default to pulse dialing – ain’t nobody got time for that.
If I “CALL” a number, it hangs up immediately after dialing, and I need to quickly enter “TERM” mode to hold the line and interact with the remote system. More exploration is needed…