Operating instructions

102 Operating the LED Display STS2
14.1.4 Button Definitions
The following table defines the buttons illustrated in Figure 50 and Figure 51.
An optional key lock switch may also may be installed.
14.1.5 Key Lockout Switch
An optional key lockout switch for the STS2 enables or disables all push button inputs, except for
the alarm silence button. The key lockout switch is mounted on the front of the unit. See
Figure 8 on page 26 to Figure 10 on page 28 for the key lockout switch location on each unit.
• To disable the buttons, turn the key to the top of the switch, toward the closed padlock icon.
• To enable all of the buttons, except the alarm silence, turn the key to the horizontal position,
toward the open padlock icon.
Figure 52 Key Lockout Switch.
ALRM Alarms A red LED is lit when an alarm
condition is present in the STS2.
Connect a PC terminal to the STS2
to locate the exact cause. See
Communication Interfaces for PC
terminal commands.
Table 17 Push button Switches—Defined
Button Definition Action
SW_PREF1 Source 1 Preferred Push this button to select Source 1 as the preferred source.
SW_PREF2 Source 2 Preferred Push this button to select Source 2 as the preferred source.
ALRMRST Alarm reset Push this button simultaneously with the NOAUD button to reset
an alarm condition. An alarm can only be reset if the hardware
condition permits a reset.
NOAUD Silence Push this button to turn off the horn that is sounded for an alarm.
This button does not reset an alarm condition, unless pushed
simultaneously with the ALRMRST button.
Note: An optional key lockout switch also may be installed.
Table 16 LEDs—Defined
LED Item Monitored Action
Changes disabled
Changes enabled