HandKey II Installation and Operation Manual
Revision 2.0 Page 17
Inputs and Outputs
In addition to the Lock and Auxiliary Output and the Card Reader Emulation Output,
the Hand Reader has additional inputs and outputs for use with alarms and other
controllers.
• Three Programmable Auxiliary Outputs
• Door Monitor Switch Input
• Request to Exit Input
• Card Reader Input for Wiegand or Magnetic Stripe
• Two Auxiliary Inputs
An open collector transistor driver drives each one of these outputs. Open collector
refers to a transistor configuration capable of sinking current (by “pulling down” one
side of a load to ground) but not able to source current – e.g. the transistor output is
incapable of supplying current to drive up the output voltage and must rely on an
external voltage source to accomplish this.
Hand Reader outputs, when measured to ground, generally show around 4.5 volts
when they are inactive and no load is attached. This voltage is developed by a
combination diode and series resistor pull up to the internal +5 volt supply of the Hand
Reader. These outputs are pulled up internally to insure that they remain in a known
condition if used to output Wiegand or magnetic stripe data to some external device.
If one of the outputs is shorted to ground, there will be approximately 5 mA of current
flowing through the short, but no damage will occur. Because of the open collector
structure of the outputs, each output is free to float to whatever external voltage is
applied (when inactive). For example, if one side of a relay coil is connected to an
external +12 volt power source and the other side of the relay coil is measured with
respect to the ground of the external power source, the measurement will be +12 volts.
If the ground of the external power source (+12 volt return) is tied to the ground of the
Hand Reader, and the free relay coil wire connected to the LOCK output, the LOCK
output pin will read +12 volts also (when inactive). This is because the LOCK output
is not active and free to “float” to whatever external voltage is applied. When a hand is
verified, the LOCK output becomes active and essentially looks like a short to the
Hand Reader ground. This “short” causes the full +12 volts of the external power
source to be placed across the relay coil, energizing the relay. The ground of the
external +12 volt source must be tied to the Hand Reader ground to make a complete
circuit path.
All Hand Reader outputs are rated at +24 volts DC maximum with a maximum current
draw of 100 mA. This means that it is acceptable to use up to a +24 volt DC external
power supply to energize external devices. Whatever external relay is used should be
chosen to match the external power supply voltage. For example, if the external relay
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