2.0 Planning an Installation
HandKey II Installation and Operation Manual
Planning an Installation
Site Preparation
Before you begin installation, check the site blueprints, riser diagrams, and
specifications for important information about hand reader location and other systems
that connect to the Hand Reader. Look for any existing wall preparations and wiring
that other contractors may have installed for the Hand Readers.
Hand Reader Placement
The recommended height for the Hand Reader platen is 40 inches (102 cm) from the
finished floor. The Hand Reader should be out of the path of pedestrian and vehicular
traffic, and convenient to, but not behind the door it is controlling. Avoid placing the
Hand Reader where users must cross the swing path of the door. The Hand Reader
should be in an area where it is not exposed to excessive airborne dust, direct sunlight,
water, or chemicals.
40 in. (102 cm.)
Figure 2-1: Hand Reader Placement Rules
For the following sections, Recognition Systems does not supply hardware items such
as door control relays, door locks, switches, relays, communications or power wiring,
or power supplies (a PS-110 or PS-220 power supply can be purchased from
Recognition Systems to power the Hand Reader).
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Four basic circuits typically connect to the Hand Reader:
• Power Input
• Door Control Inputs and Outputs
• Networking and Communications
• Card Reader Input and Emulation Output
Power Input
The Hand Reader requires 12 to 24 volts DC (600 mA) or 12 to 24 volts AC (7 watts).
Power can be connected either to terminals 1 and 2 on the terminal strip or through
barrel jack J12.
Terminal 1 and the center pin of jack J12 are connected together. Terminal 2 and the
sleeve of jack J12 are connected together.
A full-wave bridge rectifier input structure is used in the power supply of the Hand
Reader, making the polarity of terminals 1 and 2 irrelevant. Recognition Systems
recommends using terminal 1 for positive (+) voltage and terminal 2 for common (-)
for consistency. If J12 is used to attach power with the optional Recognition Systems
wall-mount power supply, terminal 1 will reflect +13.8 VDC (unregulated) and
terminal 2 will be power supply common.
Neither terminal 1 or terminal 2 is connected to the Hand Reader ground.
Do not connect a HandKey's power supply to a switched duplex outlet. The HandKey
must have a constant source of power for proper operation.
Battery Backup Operation
The Hand Reader uses an internal switching regulator to obtain internal operational
power. It accepts input voltages from 12 to 24 VDC or 12 to 24 VAC at 50 to 60 Hz.
An optional power-fail protection circuit board can be attached to the main circuit
board to provide and control battery backup. The design of the internal power supply
is such that any range of the above input voltages may be used and still provide proper
battery charge voltage and battery backup operation. Switch-over to battery power is
automatic and occurs when the input voltage falls to approximately 10.5 volts. At that
time the internal battery charger is disabled to save power and uninterrupted operation
continues on battery power.
When input power is restored, the Hand Reader switches off of battery operation and
the battery charger is re-enabled to recharge the battery. Battery charge voltage is set at
approximately 13.65 volts, and battery charge current is limited to approximately 50
mA. A fully discharged battery requires approximately 12 hours of charge to fully
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Additional options installed and specific configurations within the Hand Reader make
it difficult to predict precisely how long battery support will last, but in general two
hours of battery operation can be expected. While operating on battery backup due to
loss of main input power, the battery output voltage is constantly monitored by
internal circuitry. If the battery voltage reaches approximately 9.5 volts the Hand
Reader automatically shuts down. This is done to prevent full exhaustion of the
battery. A yellow indicator on the top panel illuminates to indicate that the Hand
Reader is running off of battery power. This indicator extinguishes when main input
power is restored.
Shunt J7 which is located immediately in front of the DIP switches on the main logic
board (see Figure 3-3) enables or disables battery operation on those Hand Readers
equipped with optional battery backup. If a Hand Reader does not have the optional
battery backup package installed, J7 is not used. On Hand Readers equipped with the
battery backup option, J7 allows service personnel a mechanism for disabling battery
backup operation before removal of main input power. To fully power down a Hand
Reader equipped with battery backup, remove or reposition shunt J7 so that the two
pins protruding up from the main logic board are not connected to each other. This
effectively opens the circuit, removing the battery from any internal circuitry. Main
input power can then be removed and the Hand Reader will fully shut down. Once the
Hand Reader has fully shut down, shunt J7 may be reinstalled. The design of the
power supply is such that main input power must be reapplied to re-enable the battery
protection mechanism. If shunt J7 is not properly installed, the internal backup battery
will not be charged, and in the event of a main input power loss, the Hand Reader will
shut down.
The Hand Reader with the battery backup option uses a 12 volt 800 ma/hour sealed
lead acid battery to provide backup battery power. This battery is located immediately
inside the rear panel of the Hand Reader and plugs into jack J4 on the keypad control
circuit board located in the top of the chassis.
Earth Ground and Shielding
Recognition Systems recommends that all Hand Readers be grounded with a solid,
reliable earth ground connection. This connection establishes a common ground return
point used to protect internal semiconductor devices from ElectroStatic Discharge
(ESD) and from external signal line transients. It also provides a common signal level
reference point between externally networked HandPunches. Recognition Systems
recommends that the earth ground source be identified by a qualified electrician
familiar with electrical codes as well as wiring and grounding techniques.
This is an extremely important and often overlooked aspect of hard-wired serial
communication systems. If the sending and receiving stations do not agree on the
ground reference for the signal voltages, communication errors or a total inability to
communicate may be observed. If the voltages are very different, it is even possible to
damage the units.
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The subject of grounding can be complicated, and the full circuit of a system,
including power supplies and often even the building line power wiring, must be
understood. It is strongly recommended that a qualified electrician or electrical
engineer familiar with this subject be consulted when designing the wiring of an HGU
network installation. Always adhere to any applicable electrical codes for your area.
Recognition Systems is not responsible for damage done to units due to improper
Use any one of the following ground terminals to make the earth ground connection:
8, 10, 12, 14, 18, 20, 22, 24, or 26. Do NOT use terminal 2 to establish the earth
ground connection; terminal 2 is not directly connected to ground.
26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8
7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
Figure 2-2: Earth Ground Connection Terminals
There are two standard methods for providing earth grounding to HandPunch units:
earth grounding all units (see Section on page15)
carrying an earth ground to each unit (Section on page15)
Earth ground all units when there is a good earth ground source near each unit and/or
when there are very long cable runs between units.
Carry an earth ground to each unit when there are no earth grounds convenient to the
unit and the unit’s power supply is floating.
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Earth Ground All Units
One method of establishing a ground reference is to connect each unit’s main board
ground to earth ground. Earth ground is found on the third pin on standard AC line
sockets (in the United States, this is the round one in the middle). If the building
wiring is functioning correctly, this should be a low-impedance path to a true ground,
which then serves as a common reference point for the units.
If this method of grounding the units is used, it is not necessary to connect the units in
the network together with a ground line in the communication cable. Indeed, doing so
could create ground loops—large-area loops which provide a good coupling to
external magnetic fields—which may actually compound communication problems. If
a magnetic field, such as that from a lightning strike, induces a voltage in the ground
loop, it is possible for large currents to flow around the loop, which can raise the
ground potential of some units relative to others. When the shield or the cable is
connected to any ground in this configuration, it should be connected only at one end
to prevent the formation of ground loops.
For systems with multiple units on a network, there will be a series of cables daisychained between the units, and the shield of each leg of the network should be
connected to ground at only one end. It does not matter which end. An example of this
method of grounding is shown in Figure 2-3.
Remote 2
Remote 1
RConnect the
Cable Shield to
Remote 1's
RConnect the
Cable Shield to
Remote 2's
To Next
Connect the Cable
Shield to the
Master's Ground
Do Not Connect
the Cable Shield
at this End
Do Not Connect
the Cable Shield
at this End
Do Not Connect
the Cable Shield
at this End
Figure 2-3: Communication Shielding With All Units Earth Grounded
All units are connected to the same earth ground. Each shield ground is connected to
only one unit, then interrupted to prevent the formation of ground loops. Two sets of
lines are wired as shown in Figure 2-3. It does not matter significantly which unit’s
GND is used for a particular shield, as long as the path is broken from unit to unit.
Carry a Ground Line to Each Unit
The second method of establishing a ground reference in a system with floating power
supplies is to use the ground line in the RS-422 cable to establish a common reference
voltage for the communication signals. This line should be connected to the negative
power terminal on the data converter or the ground line in the RS-232 port from the
host PC system. It should then be carried to one of the ground terminals on the back of
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HandKey II Installation and Operation Manual
each unit in the network. An example of this method of grounding is shown in Figure
Remote 2
Remote 1
To Next
Connect the Cable
Shield to the
Master's Ground
Connect Both Shields
to Remote 1 Ground
Connect Both Shields
to Remote 2 Ground
Connect Shield
to Next Remote
Figure 2-4: Communication Shielding Carrying a Single Ground to Each Unit
If no earth ground is available at the units, this is the only possible method of
connecting the grounds. Even if an earth ground is available, depending on the
building’s power wiring and other environmental issues, this method may be superior
to the previous one, since it establishes the ground of each unit independently of the
building power lines. Local variations in grounds between buildings, or from one point
to another in a very large building, (perhaps due to elevator motors or other largecurrent drawing machines) will have no effect on the communication network if this
configuration is used.
However, the power supplies must be truly floating, with no hidden paths back to the
high-voltage side of the transformers, or to earth ground. Since this is difficult to
achieve (there is always some parasitic capacitance between the primary and
secondary in any transformer), this method may be more susceptible to high-frequency
transients in the high-voltage side of the power lines than the earth-grounded method.
The master unit’s ground establishes the ground for the entire system. The main board
ground points are connected to the shield ground at each unit, but are not connected to
earth ground. The ground point on the master can be the data converter power supply
negative terminal, or the GND pin on the RS-232 cable. If the master is an HGU, its
main board ground can be used. This configuration should only be used if the power
supplies to the units are truly floating, otherwise ground loops will be created, and
differences in local grounds may cause large currents to flow through the cable shield.
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