Technical information

1.1.2.2 Brightness Control
The brightness control is on the face of the display. To increase
brightness, move the control 3 from left to right. On some older
models, the brightness control is on the left side. To increase the
brightness, move the control from back to front. All brightness controls
have a center detent position (midpoint).
PS/2 Displays Maintenance Manual
Brightness Control
¦ Copyright IBM Corp. 1993
1.1.2.2 - 1