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This is the connector configuration fitted as standard to the Nascom 3.

Nascom 2 and S serial printer connections

Serial printers (and keyboard terminals) are connected to the Nascom 2 via the PL2 connector. External connection to the computer should use a 25-way D-type socket, which is connected to PL2 as follows:

Pin 8 of PL2 should be connected to TP3 on the rear of the board for use as a ‘handshake’ line.

** The printer handshake at this pin is only at TTL (5 volt) level. Since many printers use a 12 volt handshake connect the grey wire from pin 8 to a diode (eg 1N4001), the other end of which is connected to another diode and a 1K resistor. The other end of the second diode is connected to pin 7 of the D-type, and the other end of the resistor is connected to pin 20 of the D-type. The cathodes of the diodes (usually marked with a bar) are connected together. This is the connector configuration fitted as standard on Nascom 3.

* These connections are suitable for the normal printers operating on RS232 and V24 signal levels, ie +12V and −12V. For printers using 2OmA current loop the input to the computer should be connected to PL2 pin 9 instead of 3, and the 20mA output to PL2 pin 12 instead of 6.

Please refer also to the data sheet ‘Use of printers with Nascom 2 and 3’ (Application Note AN-006)

Nascom 2 and 3 parallel port connections

The recommended connection between the Nascom 3 parallel PIO port, PL4, and an external connector is by means of a Scotchflex cable, using a 25-way ‘D-type’ socket for the external connection. The D-type should also be of Scotchflex type, the