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Determining the serial port protocol of a typewriter

How can i determine the serial protocol of a electric typewriter? some electric typewriters have a serial port in the back and it is a shape that is not commonly used today. I am planing on interfacing the typewriter with a Arduino and using it as a printer.

How do i determine things such as the baud rate, the pinout and the voltage. I already broke one typewriter trying to find out the protocol, I cannot get a owners manual for the typewriters, all of the other guides that i found involved modifying the circuit board and connecting the wires to the keys. I have not been able to find out how a a typewriter with a serial port works.

Here is a picture of the serial port, what type is it?

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