2-2
2.2.3
When pressed, the alarm button latches to continuously
transmit the alarm signal. The alarm transmission continues
until the button is pressed again to reset.
2.2.4
The transmitted signal is ultrasonic (very high frequency
sound), consisting of two different but precise signals in a
preset modulation pattern. Figure 2-1 shows the transmitter
block diagram. The approximate frequency of each signal is 40
kHz. Two frequencies are used to reduce the nuisance alarms
that have plagued earlier ultrasonic alarm systems. An
ultrasonic frequency is chosen because the signal will not
penetrate walls and, therefore, provides the location of the
person in trouble.
BATTERY
OSC.
POWER
AMPLIFIER
TRANSDUCER
SWITCH
ENCODER
Figure 2-1 Transmitter Unit
2.2.5
Battery power for the PAT/S is provided by a Lithium battery
capable of providing power for up to 100 hours of continuous
transmitting time or several years in normal operation. The
PAT/C is powered by A 9V Lithium battery pack which provides
an operating life of about 1 year.Battery voltage is constantly
monitored, and a low battery indication is given when battery
capacity falls below a preset limit. However, the battery life
should not be relied upon without periodic testing. Magal-