©2006 Cypress Computer Systems,Inc. • www.cypressworld.com
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Using Auxiliary Inputs and Outputs: Digital Inputs
Direct connections to the Auxiliary I/O operate at a maximum of +5 Volts. They can be
used with most standard system control voltages using the techniques discussed below.
The Digital I/O signals can interface directly to panels and readers that use 5 Volt signal levels. Each Digital I/O
point is capable of sinking 25 mA of current. Application of voltages greater than 5 Volts can damage the board.
The digital inputs are pulled up to +5 Volts and operate as active low, they will operate when connected to
ground ( 0 Volts ). They can be driven by a digital output from a panel or reader, by an open collector output, or
by a relay contact connected to ground.
In no case should a Positive voltage greater than 5 Volts ever be applied to the digital inputs.
Here are several examples of driving the Suprex-1200 series digital inputs using standard field wiring practices.
Activating a digital input with relay or switch contacts.
Digital Input
Ground
Ground
Digital Input
Open Collector Output
Activating a digital input with open collector output device.
