Section II. DETAILED FUNCTIONAL OPERATION

b. When not operating in conjunction with a

processor/transceiver ultrasonic motion signal, the

band rejection filter is inserted between the broad-

detection circuits process the output from the

band amplifiers and the detection circuits. A syn-

broad-band amplifier without going through the

chronizing pulse of 26.3 kHz (provided by the

band rejection filter. The detection circuits recognize

processor/transceiver ultrasonic motion signal) is

a high frequency sound of 50 msec duration or longer.

also connected to the band rejection filter. A sharp

Four detected high frequency sounds of 50 msec

rejection notch filter is generated at the precise

duration occurring within a 15 second period will

frequency of the processor/transceiver ultrasonic

activate the alarm or a single continuous high

motion signal therefore any ultrasonic sounds

frequency sound of 4.5 seconds duration or longer

generated by the transmit transducer (transceiver)

will also activate the alarm.

are filtered out and not processed by the detection

circuits. High frequency sounds adjacent to either

c. When the processor/receiver ultrasonic passive

side of the filter notch pass through and are

signal is operating in the same area as a

processed by the detection circuits.

Section II.

DETAILED FUNCTIONAL OPERATION

6-3. Detailed Functional Analysis (fig. FO-2)

circuit that is resonant at approximately 26 kHz (mid

way in the equipment ultrasonic range). The

Detailed block diagram of the processor/receiver

combined resonant circuits of the three broad-band

ultrasonic (fig. FO-2, located at rear of manual)

amplifiers results in a relatively flat frequency

highlights the functions within the receiver and the

response between 20 kHz and 30 kHz and rejects

processor as well as signal flow paths between

frequencies outside of this band that are associated

functions. Blocks are identified by their function and

with naturally occurring phenomena.

the main components comprising the function.

a. Receiver. This unit contains an ultrasonic

c. Detection Circuits. W h e n o p e r a t i n g a

microphone and a preamplifier. The microphone is a

processor/receiver ultrasonic passive signal without

sensitive and delicate component and should be

a processor/transceiver ultrasonic motion signal

handled with care. It has a flat frequency response

operating in the same environment, the band

between 20 kHz and 30 kHz and contains an integral

rejection filter is bypassed and broad-band amplifier

FET buffer amplifier. The microphone drives

Q3 is coupled directly to amplifiers Q8 and Q9. These

preamplifier Q1 which is in cascade with broad-band

two amplifiers are direct coupled and provide

amplifier Q1 in the processor. The preamplifier has

additional gain for driving envelope detector CR1.

an adjustable gain of 20 dB which is controlled by

Output from envelope detector CR1 is impressed on

GAIN control R7 for setting optimum levels as

the base of threshold detector Q10 which operates at

required at each receiver location. The output

approximately plus 0.6 volts and fires one shot

impedance of each receiver is very high compared to

multivibrator Q11 and Q12. The output pulse from

the input impedance of broad-band amplifier Q1

the one shot multivibrator (test point MV) will

(processor). With multiple preamplifiers connected in

persist for approximately 1.5 seconds (momentary

parallel, the combined impedance of the worst

threshold exceeded) or for a threshold exceeded

condition (twenty) will not swamp the input to

period plus 1.5 seconds (fig. 6-2). During no detected

broad-band amplifier Q1.

sound the voltage level at test point MV is

b . B r o a d - b a n d A m p l i f i e r s . The input to the

approximately zero and during detected sound the

voltage level at test point MV rises to approximately

processor, from the preamplifier (receiver), is coupled

into broad-band amplifier Q1 which has a parallel

11 volts (length of voltage present is determined by

fixed tuned L-C circuit that is resonant at approxi-

one shot multivibrator). Integrator gate Q13 is

normally conducting when one shot multivibrator is

mately 22 kHz (low end of the equipment ultrasonic

inactive and when in this state it discharges R-C

range). The output of Q1 is coupled into the second

broad-band amplifier (Q2) which has a parallel fixed

integrator R48 and C27. When the one-shot multivi-

tuned L-C circuit that is resonant at approximately

brator is activated, integrator gate Q13 is cut off and

the R-C integrator starts charging. Following the

30 kHz (high end of the equipment ultrasonic range).

prescribed detected duration period of sound, the R-C

A swamping resistor is connected across this parallel

L-C resonant circuit to broaden the response curve.

integrator reaches a threshold level of approxi-

Output from Q2 is coupled into the third broad-band

mately 3 volts. Threshold detector Q14 goes into

conduction and operates one shot multivibrator Q15

amplifier (Q3) which has a parallel fixed tuned L-C

6-2