Keri Systems SB-293 - Manual (Page 32)

Technical Reference Manual – PXL-250 and SB-293 Keri Systems, Inc.
Page 32 P/N: 01836-004 Revision 5.5
8.0 Understanding Inputs and Outputs
The following section provides descriptions of all Inputs and Outputs on the PXL-250
Controller and the SB-293 Satellite board. Wiring diagrams for all inputs and outputs
are included in the next section, Wiring Connections beginning on page 39.
8.1 Inputs
An input detects a state change generated by a device outside of the controller. The
controller then responds to that state change per commands programmed by the Doors
program. The input devices that generate the state change may be normally closed or
normally open.
A normally closed input device continually keeps a circuit closed or complete. A state
change is generated when the normally closed input device is opened, breaking the
circuit. In an access control system, a door switch is a typical example of a normally
closed device. While the door remains closed, the switch remains closed. When
someone opens the door, the door switch is opened, breaking the circuit and generating
a state change. The controller then responds to this state change per programmed
instructions and generates an output such as sounding an alarm if the door is a secure
door.
A normally open input device continually leaves a circuit open or incomplete. A state
change is generated when the normally open input device is closed, completing the
circuit. In an access control system, a request-to-exit (RTE) button is a typical example
of a normally open device. In an access control installation, an RTE button is located
on the secured side of the door. While there is no one at the door pressing the button,
the switch remains open. When someone desires to exit through a secure door, they
press the RTE button, closing the circuit and generating a state change. The controller
then responds to this state change per programmed instructions and generates an
output such as unlocking the door to allow exit.
8.1.1 Door Status Switch Input
The door status switch input accepts a signal from a normally closed input switch that
indicates the status of the door: open or closed. While the door remains closed, the
switch remains closed. When someone opens the door, the door switch is opened,
breaking the circuit and generating a state change. The controller responds to this state
change per programmed instructions and generates an alarm output if the door is
forced open or is held open too long. Refer to Figure 9-8 on page 49 (for the PXL-250)
and Figure 10-10 on page 82 (for the SB-293) for possible Door Status Switch wiring
diagrams.
NOTE: A door switch must be installed on any door to which anti-passback is being
applied. This allows the controller to properly track the anti-passback feature in the
Doors program.