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Hardware Installation Guidelines
1.2
Alarm Inputs
1.2.1
Unsupervised Alarms
Unsupervised alarm inputs sense simple contact closure. Open circuit results in an alarm condition. These
inputs are protected by pull-ups, series limiting resistors, and clamp diodes against transients, like
ElectroStatic Discharge. The signal is then buffered to reduce the effect of noise.
Open contacts should result in terminal voltages of 3.5 to 5 VDC. Closed contact terminal voltage should be
between 0 and 0.8 VDC.
1.2.2
Supervised Alarms
Various OnGuard hardware products provide contact supervision. These inputs require an end-of-line (EOL,
1K±10%) terminator to be installed with the contact to be monitored. This can be configured within the
software. Input protection is similar to that of the unsupervised input, however the input is also filtered to
reject 50/60 Hz AC coupling.
The supervised input can sense contact conditions of SAFE, ALARM, and FAULT. It also accommodates
normally closed (NC) and normally open (NO) contacts, which is configurable within the application.
1.3
Reader Inputs/Outputs
1.3.1
Reader Data Input
Reader data input is similar to unsupervised alarm input. Reader data input interfaces to reader DATA 1/
DATA 0 (WD1/WD0) open collector signals and produces a nominal signal swing of 0 to 5 volts.
1.3.2
Open Collector Output
Open collector output is used by readers to send reader data DATA1/DATA0 (WD1/WD0) and to control
external LEDs. Pull-up resistors and diode clamps are provided for reader data outputs. This type of
interface is limited to 500 feet.
1.4
Relay Outputs
Some Lenel hardware products provide form C relay contact outputs. These are dry contacts that are capable
of switching signals as well as higher current loads. However, once they are used to switch current (for
example, a door strike), they can not be used reliably to switch small signals (for example, dialer input.)
1.5
RS-485 Communication Overview
The EIA RS-485 standard defines an electrical interface for multi-point communication on bus transmission
lines. It allows high-speed data transfer over extended distance (4000 feet/1219 m.) The RS-485 interface
20 —
revision 7
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