NorthStar HORIZON Manual page 73

the standard serial interface (4D for the second serial
interface) should be jumpered as follows:
Connect pin 1 to pin 16
Connect pin 2 to pin 12
Connect pin 3 to pin 14
Connect pin 4 to pin 15
Connect pin 5 to pin 13
Connect pin 7 to pin 10
Connect pin 8 to pin 9
Note: Space is provided on the motherboard for adding additional
resistors and capacitors (R10-13, R18-21, R26-29, C23-26, C31-34,
and C39-41) for connecting to the "response control" inputs of
the RS-232 receivers. Refer to a 1488 data sheet for details.
CURRENT LOOP CASES
To configure a serial interface for current loop operation
proceed as follows:
a. Connect a 2N3904 transistor to a 14-cin DIP header with the E
lead connected to pin 7, the B lead connected to pin 5 and the
C lead connected to pin 6.
b. Connect a 5.6K ohm 1/4 Watt resistor (green-blue-red) between
pins 4 and 12 on the header.
c. Connect a lK ohm 1/4 Watt resistor (brown-black-red) between
pins 8 and 14 on the header.
d. Remove the 1488 at location 3B Standard (4B Second), and
replace it with the header just built.
e. Take a 16-pin DIP header and make the following connections.
Connect pin 6 to pin 7 and pin 8
Connect pin 9 to pin 10
Connect pin 12 to pin 16
f. Install the 16-pin header just built at location 3D (standard
serial interface), or 4D (second seri.al interface).
g. Wire the current loop for the printer part of the device being
interfaced to the 25-pin serial interface connector pins 3(-)
and 9(+). Wire the keyboard current loop to connector pins
2 (+) and 10 (-) .
73
North Star HORIZON Computer