Parallel Relay Interface Port Schematicauthoritative a broadcast from the PC's alongside printer anchorage (LPT1 or LPT2). Amount A shows a solid accompaniment broadcast controlled by one of the alongside anchorage abstracts curve (D0-D7) application a 300 ohm resistor and 5 volt ability source. The solid accompaniment broadcast will animate back a "0" is accounting to the abstracts line. Amount B and C appearance automated relays controlled by two transistors. The broadcast in amount B is activated back a "1" is accounting to the abstracts band and the broadcast in amount C is activated by autograph a "0" to the line. In anniversary of the three circuits, a accepted affiliation is fabricated from the abrogating ancillary of the ability accumulation to one of the anchorage arena pins (18-25).
There are three accessible abject addresses for the alongside anchorage You may charge to try all three abject addresses to actuate the actual abode for the anchorage you are application but LPT1 is usually at Hex 0378. The QBasic "OUT" command can be acclimated to accelerate abstracts to the port. OUT, &H0378,0 sets D0-D7 low and OUT, &H378,255 sets D0-D7 high. The alongside anchorage additionally provides four ascendancy curve (C0,C1,C2,C3) that can be set aerial or low by autograph abstracts to the abject address+2 so if the abject abode is Hex 0378 again the abode of the ascendancy latch would be Hex 037A. Note that three of the ascendancy $.25 are astern so autograph a "0" to the ascendancy latch will set C0,C1,C3 aerial and C2 low.
