User's Manual

US7,420,471; US8,169,335; US8,232,888; US5,939,986;
US6,810,353; AU2005289704; ZA2007/02919; ZA2008/02673;
ZA2010/06816, ZA2010/09068 Patent Pending
1 Overview
The Personal Alarm Device is part of a complete HIT-NOT Proximity Detection system from
Frederick Energy Products which provides warnings to both individuals and to vehicle operators
to alert them that the individual has entered too close to an operating piece of equipment and
is in a dangerous situation. The Personal Alarm Device is worn by the pedestrian to alert them
of impending danger. There are two models of the DDAC-PAD that are functionally identical except for
the location of an audible sounder. The sounder for the Model DDAC-PAD is located in the PAD housing;
whereas the sounder for the Model DDAC-PAD-XL is at the end of a cable extending from the housing.
The DDAC-PAD-XL model has a louder (103 dBA) sounder for use in areas with loud background noise
that require extra hearing protection
1.1 Theory of Operation
The functions of the Personal Alarm Device are:
• To sense the 73 kHz field generated around a vehicle or piece of machinery equipped
with a Magnetic Field Generator.
• To echo a signal back to the Magnetic Field Generator to confirm signal recognition.
• To transmit a 916.48 MHz RF signal to the Magnetic Field Generator.
• Turn on its own alarm when the 73 kHz signal from the Magnetic Field Generator is
confirmed.
When a Personal Alarm Device (PAD) is in close proximity of the Magnetic Field Generator, the
PAD will detect the 73 kHz magnetic field from the generator and analyze its field strength.
When the 73 kHz field strength received by the PAD is above a certain threshold it will indicate
that the distance of the Magnetic Field Generator is close enough to the PAD to signify a
Warning or Danger condition. The PAD is calibrated to differentiate the magnetic field into two
zones: Warning and Danger. The PAD will echo back to the Magnetic Field Generator with a
916.48 MHz transmission to confirm the signal recognition and then send the alert to the
Magnetic Field Generator. The Magnetic Field Generator has its 916.48 MHz receiver ON when
it is transmitting the 73 kHz field and is “listening” to receive any 916.48 MHz transmissions
from a pedestrian with a PAD to indicate the individual is too close to the vehicle and warrants
a warning or danger condition. When an alert condition has been confirmed between the PAD
and Magnetic Field Generator, the PAD will activate its own alarm. The signal in the Warning
Zone will activate an LED light and the sounder will give an alarm in a series of 3 beeps. If the
pedestrian is in the Danger Zone, they will receive a continuous alarm from the sounder and the
LED light.
1.2 Frequency of Operation
The Personal Alarm Device will receive on a frequency of 73 kHz and transmit on a frequency of
916.48 MHz.
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