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Pelco Manual C690M-E (11/04) 19
CONNECTING ALARMS
On the rear panel of the unit are four 8-pin inputs. Every odd-numbered pin is an alarm pin
while every even-numbered pin is a ground. These inputs can be configured to be N.O.
(normally open), N.C. (normally closed), or supervised.
• Unsupervised relay contacts are wired as either normally open or normally closed.
Unsupervised modes are easily defeated and should not be used in critical situations
when security is most important.
• Supervised mode activates an alarm if the current in a line falls outside a specified range.
This blocks an attempt to defeat the alarm system by cutting a wire or through bypassing
or shorting a section of the circuit.
Inputs are configured via a DIP switch mounted next to the connectors, as follows:
• If switch 1 (counting from the left) is up, then alarm mode is supervised.
• If switch 1 is down, then alarm mode is unsupervised (will be N.O. or N.C.).
• If switch 2 is up, then alarm mode is normally closed (N.C.).
• If switch 2 is down, then alarm mode is normally open (N.O.).
Switch 2 is irrelevant if switch 1 is up—in supervised mode the unit does not care whether
wiring is for N.O. or N.C.; it is watching for a deviation from constant current flow.