How can I plug a peripheral intended for a PC into the Psion or Nokia COM port?

The Psion and Nokia both have an unusual miniature socket for the serial port, whereas most PC’s have a 9 way male D type socket on the back. To plug a standard PC peripheral into your XTM machine you therefore need an adapter to convert from the miniature socket to a 9 way socket. Because the miniature plug is hard to buy, many people use the docking cable that came with their Nokia or Psion and make a converter for the end of that instead.

The docking cable is a null modem cable - that is, it crosses over the various input and output lines so that, for example, the Psion/Nokia transmit line is connected to the PC receive line and the PC transmit line connects to the Psion/Nokia receive line. The connections in the 9 way plug at the end are therefore the opposite of what we want. To flip the signals back to PC order, the adapter should consist of two 9 way male connectors wired as follows:

Although this shows all the connections found in a 9 pin plug, not all these signals are present in your XTM machine. The Nokia Communicator only implements the data lines (transmit and receive) - it doesn't have any modem lines - and software running under XTM will not see any modem input signals on a Nokia Communicator. The Psion family provides all the PC modem lines except for the Ring Indicate (RI) input that would appear on pin 9 on a real PC. Software running under XTM on a Psion that reads the RI bit from the UART emulation will always read it as OFF.