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PES1900NR Operations Manual
Chapter 7. Connecting External Alarms — 111
Digital Inputs
The repeater has two digital inputs, and one battery monitor input.
The two digital inputs can be used to monitor equipment or events that are external to the repeater.
These external alarms are controlled and processed through the RepeaterNet software, in the same
way as internal alarms. The severity of each external alarm input can be set.
Figure 92 shows the equivalent circuit for the external alarm inputs. The digital inputs are accessible
through connector J1 on the repeater’s connector panel.
Figure 92 Digital Input Circuit - Typical
Maximum Ratings
Do not exceed the following specifications when connecting digital inputs:
Input Voltage for Logic 0
<0.5 Volts
Input Voltage for Logic 1 (active alarm/disable PA)
>4.0 Volts
Maximum Input Voltage
5.0 Volts
Minimum Input Voltage
0.0 Volts
Maximum Input Current
2.0 mA
Tower Light Alarming
One of the most common external alarms, at a base station or a repeater site, is the failure of a tower
hazard warning light. This light, used for warning aircraft of the existence of a tower, must be
replaced immediately if it fails. Figures 93 and 94 show two ways that the external digital alarm inputs
can monitor a tower light.