PRINT POSITION INDICATOR

TM 11-7025-233-23

2-12. PRINT POSITION INDICATOR

The print position indicator (PPI) is a display device and a circuit board (fig.

2-9). In normal operation, it indicates carriage position by displaying the column

number in which the next character will be printed. At startup and when a

malfunction occurs, diagnostic codes are displayed. Operational status codes are

also displayed by the PPI (table 2-1). All displays come from the logic board.

The T3PPI circuit board on which the display LEDs are mounted contain no test

points, jumpers, or fuses. The board can be replaced.

Figure 2-9.

Print Position Indicator

Without a paper out switch, the teleprinter has no way to tell if there is paper to

print on or not. The logic therefore assumes that there will be paper and Prints

whenever there is data to print. If there is no paper, i t prints on the platen.

With a paper out switch, the paper restrains the actuating arm, holding the

contacts open. The logic sees the open contacts as meaning paper is present. When

the end of the paper passes the switch, the actuator arm is released and the

contacts close, signalling the end of the paper to the logic board. The logic

lights a P O (paper out) alarm on the PPI, stops printing, and transmits a break to

the data source.

2-8