Technical Reference Manual – SB-293
Printing Date
01838-002 Rev. 3.0
July-1998
Page 13 of 32
Auxiliary RTE Input
One of the general-purpose inputs can be configured as an auxiliary RTE input for the B-door. The
auxiliary RTE input allows a second RTE switch to be used to unlock the B-door at a controller. Using
a normally open switch as the input device, while the switch is in its normal state, the general-purpose
input circuit remains open. When a person requesting egress closes the switch, the general-purpose
input circuit is closed generating a state change. The controller then responds to this state change
per programmed instructions and generates a command to unlock the door and allow egress. Refer
to Figure 11 on page 19 for a typical auxiliary RTE input wiring diagram.
Output Relays
In many respects, a Form C output relay performs the opposite task of an input. An input detects a
state change generated by a device outside of the controller. An output relay receives a signal from
the controller that energizes the output relay, switching its state. This state change typically prompts
an action outside of the controller. The inputs drive the signals that control the output relays.
An example of this process is when a secure door is forced open. As the door is opened, the door
status switch opens. The door status switch input detects the switch's state change. The controller
sends a signal instructing the alarm relay to energize. The alarm relay switches its state to activate an
audio alarm notifying everyone in the immediate area that the door has been forced open. A variety of
devices may be activated by an output relay such as an electric door strike, a magnetic lock, an
alarm, a light, a video camera, or a modem.
A Form C relay has both normally closed and normally open circuits. When the relay is not energized,
the normally closed circuit is complete and the normally open circuit is open. When the relay is
energized the circuits switch roles; the normally open circuit is closed and the normally closed circuit
is open. This dual nature of Form C relays (having both normally closed and normally open circuits)
allows for two types of applications outside the controller. A device may be attached to the normally
closed circuit so that it is always on until the relay energizes to open the circuit and turn it off. Or, a
device may be attached to the normally open circuit so that it is always off until the relay energizes to
turn it on.
Lock Relay
Unlocking a door is controlled by the Form C lock relay. When installing a door lock there are two
things to consider: safety versus security, or should the door be "fail-safe" or "fail-secure."
Fail-safe means that if the power should fail at a door (perhaps due to a power outage or equipment
failure), the door will automatically unlock allowing entrance and egress. Power is required to keep
the door locked. A fail-safe door ensures people will be able to enter and exit a secured area through
that door in the case of an emergency.
A typical fail-safe application may use a magnetic lock. In this application, the controller energizes the
lock relay, causing the lock relay to change its state. In its new state the normally closed circuit is
opened breaking the power to the magnetic lock and allowing the door to be opened. Refer to Figure
6 on page 16 for a typical fail safe lock relay wiring diagram.
Fail-secure means that if the power should fail at a door (perhaps due to a power outage or
equipment failure), the door will automatically lock and not allow entrance but will continue to allow
egress. Power is required to unlock the door. A fail-secure door ensures a secured area remains
secure regardless of the situation.
A typical fail-secure application may use a door strike. In this application, the controller energizes the
lock relay, causing the lock relay to change its state. In its new state the normally open circuit is
closed activating the release mechanism for the door strike on the door to be opened. Refer to Figure
7 on page 17 for a typical fail secure lock relay wiring diagram.
SYSTEM INSTALLATION
