Reference Data; Controls; External Controls - IBM 3277 Troubleshooting Manual

This section contains miscellaneous reference information
that can be helpful in maintaining IBM 3277 Display
Stations.
6.1 CONTROLS
Controls are divided into two categories: external and
internal. External controls are those that are accessible
without remov ing covers. I nternal controls are those that
are under covers and are accessible to maintenance person-
nel only. The audible alarm volume control, although
located under the front cover, is considered an external
control because the display station operator can adjust the
volume.
6.1.1 External Controls (Diagram 6-1 )
6.1.1.1 OFF-PUSH (Power, Brightness, and Contrast)
The OFF-PUSH switch is a triple-function control that
adjusts the display image brightneS5 and contrast. I t also
controls display station power. Pulling the switch out
CRT Bezel
OFF·PUSH
OFF-PUSH Switch
(Power/Contrast/Brightness)
IBM
CRT
Diagram 6-1. External Controls and Indicators
Indicators (3)
Section 6. Reference Data
toward the operator turns display station power on. The
overall displayed image is made brighter by rotating the
Brightness control (outer knob) clockwise; the image is
made dimmer by rotating the knob counterclockwise. The
Contrast control (inner knob) is on a concentric shaft with
the Brightness control. Rotating the Contrast control
clockwise reduces the difference in contrast between high
and normal intensity characters; rotating the control
counterclockwise increases the difference in contrast.
6.1.1.2 Security Keylock (Optional Feature)
This operator control is a key-operated switch lock. The
key must
be
inserted in the lock and turned on (horizontal
position) to enable the display station for operation. The
key must remain in the On position to keep the display
station enabled. The key cannot be removed from the lock
unless it is returned to the Off position.
6.1.1.3 Selector Light-Pen Tip Switch (Optional Feature)
The selector light-pen contains a spring-loaded switch in its
tip. The switch is used to select detectable fields on the
SYSTEM
AVAILABLE
INSERT
MODE
INPUT
INHIBITED
Security Key
Reference Datil 6-1