Testing apparatus for intrusion detectors

The monitoring of intrusion detectors is effected by an apparatus for testing the responsiveness to environment-caused, detector-specific useful and spurious signals. This testing apparatus is arranged inside of the intrusion detector and ensures that during installation and during the operation of the intrusion detector its electrical parameters are optimally adjusted. Deviations of these parameters from their nominal values and the location of these deviations are indicated.

BACKGROUND OF THE INVENTION 
The present invention relates to a new and improved apparatus for testing 
the responsiveness of an intrusion detector to environment-caused and 
detector-specific useful and spurious signals and for locating the 
electrical parameters which deviate from the nominal value. 
Presently it is known that, for monitoring objects such as, for example, 
factories, administration buildings, stores, exhibition buildings, 
shopping centers, banks, open areas, parking areas, airports and so forth, 
systems are used which detect the intrusion of intruders and direct an 
intrusion alarm signal to the group of persons responsible for the 
protection of these objects such as, for instance, security forces or 
police. The monitoring systems contain a multitude of intrusion detectors 
which are distributed over the large-area object. These intrusion 
detectors are connected to a central station or a number of sub-central 
stations which, on response of the intrusion detector, generate the alarm 
and pass it on to the object protectors. The intrusion detectors are 
constructed as infrared detectors, ultrasonic detectors, microwave 
detectors, sonic detectors, vibration detectors, as well as capacitative 
detectors. These intrusion detectors commonly respond to 
environment-caused or detector-specific signals. Intrusion-specific 
signals such as those, for instance, due to the movement of persons, due 
to the noise of breaking glass, or due to mechanical action upon walls and 
objects, generate an electrical signal level in the intrusion detector. 
This electrical signal level in the intrusion detector totally or 
partially reaches the alarm threshold depending upon the distance of the 
intrusion detector from the event or happening. THe intention is that at 
least that intrusion detector will respond which is closest to the event 
or happening. An alarm is only generated if a predetermined threshold 
level is exceeded. The intrusion detectors also respond to spurious 
signals. Environment-caused spurious signals are, for instance, noises, 
air turbulences, temperature fluctuations and so forth. Detector-specific 
spurious signals are, for instance, sensor noise and so forth. When the 
spurious signals i.e. the environment-caused spurious signals or the 
detector-specific spurious signals, reach a certain level, the danger of 
false alarms will increase. 
Furthermore, false alarms can occur when components of the intrusion 
detector deviate from their nominal operating values due to aging, 
intolerable environmental influences, such as for instance, condensation, 
vibrations, sabotage actions, and so forth. These false alarms can be a 
direct result of these deviations. Furthermore, environment-caused 
spurious signals which are normally suppressed may trigger false alarms 
due to a parameter deviation in certain components. 
In U.S. Pat. No. 3,383,678, an intrusion detector for detecting movement is 
described which operates according to Doppler Principle. In this patent 
there is also described a function control of the electrical components of 
the intrusion detector. This function control is carried out in such a 
manner that a portion of the transmission power is coupled-out before the 
antenna and infed via a "motion simulator" at the output of the receiving 
antenna. The object of the "motion simulator" is to simulate the movement 
of an intruder and to thereby check the function of the electrical part of 
the intrusion detector during the presence of an intrusion signal. 
However, during this check on the operability of the intrusion detector, 
there can not be determined to what extent individual components of the 
intrusion detector have deviated from their nominal values. By means of 
this test there has only been determined the response of the intrusion 
detector to movement influences. The response of the intrusion detectors 
during disturbances thereby is not yet tested. The latter implies that the 
intrusion detector is prone to false alarms. It is noted as a further 
disadvantage that the check discribed hereinbefore does not permit a 
localization of the fault in the electrical circuit. The described check 
is a mere function check which can only be carried out during the 
operation of the intrusion detector. 
SUMMARY OF THE INVENTION 
Therefore, with the foregoing in mind, it is a primary object of the 
present invention to provide a new and improved construction of a testing 
apparatus for intrusion detectors which does not exhibit the 
aforementioned drawbacks and shortcomings of the prior art constructions. 
Another and more specific object of the present invention aims at providing 
a new and improved construction of a testing apparatus of the previously 
mentioned type for testing the responsiveness of an intrusion detector to 
environment-caused, detector-specific useful and spurious signals and for 
locating the electrical parameters which deviate from the nominal value. 
A further important object of the present invention is directed to a new 
and improved construction of a testing apparatus to monitor an adjustment 
of the variable parameters, e.g. sensitivity, integration time, band-pass, 
threshold values, and other values that require adjustment prior to 
setting the intrusion detector into operation at its location and under 
consideration of the environment to be monitored. 
At the same time, a further important object of the present invention is 
directed to a new and improved construction of a testing apparatus 
permitting to detect parameter deviations already before these lead to a 
concrete false alarm or non-detection of an intrusion. In this manner, 
intrusion defective operations of the detector are intended to be avoided 
by means of early diagnosis. 
Apart therefrom, a still further significant object of the present 
invention is directed to a new and improved construction of a testing 
apparatus in which the early diagnosis is intended to indicate the fault 
location in the electronic circuit of the intrusion detector. 
Yet a further significant object of the present invention aims at providing 
a new and improved construction of a testing apparatus of the character 
described which is relatively simple in construction and design, extremely 
economical to manufacture, highly reliable in operation, not readily 
subject to breakdown or malfunction and requires a minimum of maintenance 
and servicing. 
Now in order to implement these and still further objects of the invention, 
which will become more readily apparent as the description proceeds, the 
testing apparatus of the present invention is manifested by the features 
that a signal generator is provided for generating test signals, together 
with an electronic evaluation circuit having inputs and selected 
coupling-out outputs. A first switching arrangement selectively applies 
the test signals to desired inputs of the electronic evaluation circuit. A 
second switching arrangement selectively couples-out the resultant signals 
generated by the test signals. Finally, a logic control circuit compares 
the resultant signals with the correct signals and indicates, at the 
occurrence of a fault in one of the resultant signals, the fault location 
at indicating means. 
The invention relates to active intrusion detectors such as ultrasonic 
detectors, microwave detectors and capacitative detectors and passive to 
intrusion detectors such as infrared detectors, sonic detectors and 
vibration detectors.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Describing now the drawings, it is to be understood that to simplify the 
showing thereof, only enough of the structure of the testing apparatus for 
intrusion detectors has been illustrated therein as is needed to enable 
one skilled in the art to readily understand the underlying principles and 
concepts of this invention. Turning now specifically to FIG. 1 of the 
drawings, the apparatus illustrated therein by way of example and not 
limitation, will be seen to comprise an acitve intrusion detector 10 in 
schematic illustration. A sensor or receiving device receives signals from 
a space 2 to be monitored or from an intruder or object 3, to be 
monitored, respectively and converts these into electrical signals in an 
electronic evaluation circuit 5. Such electronic evaluation circuits 5 are 
generally known to the art. Therefore, the electronic evaluation circuit 5 
is not further described in connection with FIG. 1. Such an evaluation 
circuits 5 generates at its output 6A an alarm signal 7 when the signals 
received at the sensor or receiving device 1 indicate intrusion 
activities. With reference to FIG. 1 it will now be demonstrated that the 
invention, namely the monitoring of electrical parameters at various 
locations in the evaluation circuit 5, can be used for active intrusion 
detectors. As already mentioned, ultrasonic detectors, microwave 
detectors, and capacitative detectors are designated as active intrusion 
detectors. These intrusion detectors have a transmitter or transmitting 
device as well as a sensor or receiving device. A logic control circuit 8 
drives switching devices or switches 91, 92, 93 into the illustrated 
positions via the lines. The transmission signal generator 94 can now pass 
its transmission signal having the transmission frequency f.sub.o via the 
closed switching devices or switches 93, 91 to a transmitter or 
transmitting device 4 which radiates this transmission signal having the 
transmission frequency f.sub.o into the space 2 to be monitored. The 
radiation reflected by the intruder or object 3 to be monitored is 
received by the sensor or receiving device 1 and processed in the 
subsequent electronic evaluation circuit 5. 
If now, during installation, the intrusion detector 10 must be adapted to 
the peculiarities characteristic of the space 2, this is effected by 
adjusting the corresponding parameters in the evaluation circuit 5. This 
will now be further explained hereinbelow. The logic control circuit 8 
drives the switch or switching device 91 via the control line or conductor 
81 in such a manner that the transmitter 4 is disconnected from the 
transmission signal generator 94. The logic control circuit 8 drives the 
switch or switching device 92 via the control line or conductor 82 in such 
a manner that a test signal generator 90 is connected with a first 
switching arrangement constituting a multiplex switch or multiplexer 96 
via modulating means constituting a mixer stage 95. Such test signal 
generator 90 may be constructed to generate test signals of any one of the 
following shapes: substantially triangular, rectangular, saw-tooth or 
trapezoidal pulses or substantially sinusoidal oscillations. In the mixer 
stage 95 the test signal having the test frequency f.sub.x and generated 
by the test signal generator 90 and the transmission signal having the 
transmission frequency f.sub.o of the transmission signal generator 94 are 
received on the input side 95A in order to produce modulated test signals 
on the output side 95B of the mixer stage 95. These modulated test signals 
are now selectively applied to desired inputs, for example, the inputs 7A, 
7B and 7C associated with selected input locations of the evaluation 
circuit 5 according to a predetermined program which is stored in the 
logic control circuit 8. The logic control circuit 8 drives the 
corresponding switches or switching devices in the multiplex switch or 
multiplexer 96 via a control or conductor 84 such that they are closed. 
Only input locations 51 and 52 of the input locations of the evaluation 
circuit 5 are shown in FIG. 1 and these input locations 51 and 52 are 
respectively connected to the input side 53A and the output side 53B of a 
component, namely a current circuit 53 of the electronic evaluation 
circuit 5. For example, the sensitivity of the intrusion detector 10 for 
the related space 2 to be monitored is intended to be adjusted to optimal 
conditions by means of adjusting a variable parameter of the current 
circuit 53. For this purpose, modulated test signals of the type as shown, 
for example, in FIGS. 3, 5 6, are first supplied to the input 7B 
associated with the input location 51. In this connection, it is also 
pointed out that the logic control circuit 8 has driven a second switching 
arrangement constituting a multiplex switch or multiplexer 97 via a 
control the line or conductor 85 such that the resultant signals formed as 
a result of the selective application of the modulated test signals can be 
received at the outputs 6B and 6C of the evaluation circuit 5 and arrive 
via control lines or conductors 98 at the logic control circuit 8. At this 
logic control circuit 8 the modulated test signals are compared with 
respective stored reference wave trains associated with important 
resultant signals. If there is no conformity, this is indicated in the 
logic control circuit 8 by appropriate indicating means. The current 
circuit 53 is now adjusted by service personnel until the logic control 
circuit 8 indicates optimum conformity between the resultant signals and 
the stored reference wave trains. The input of modulated test signals 
signals at the input location 52 of the evaluation circuit 5 is necessary 
for checking, during operation, the components of the evaluation circuit 5 
which follow the current circuit 53, independently of the value of the 
adjustable parameter in the current circuit 53. 
In the following description, it will now be assumed with reference to FIG. 
8 that the intrusion detector 12 shown in FIG. 8 constitutes a passive 
intrusion detector which, as is well known in the art, does not contain 
the transmitter or transmitting device 4 but only the sensor or receiving 
device 1. The control lines or conductors 81 and 83 as well as the the 
switches 91 and 93, the signal generator 94 and the mixer stage are not 
present but were present in the active intrusion detector 10 shown in FIG. 
1. Such passive intrusion detector 12 may be constructed, for example, as 
an infrared detector, a sonic detector or a vibration detector. If now, 
during installation of the passive intrusion detector 12, the test 
operation is intended to be carried out, the logic control circuit 8 
drives the switch or switching device 92 via the control line or conductor 
82 such that the test signal generator 90 passes its test signals via the 
closed switch or switching device 92 and the dash-dotted control line or 
conductor 99 to the multiplex switch or multiplexer 96 and to the input 
location 51. The optimum adjustment of the sensitivity of the passive 
intrusion detector 12 with respect to the space 2 to be monitored with its 
particularities now follows in the same manner as already discussed in 
connection with the active intrusion detector 10. However, for the sake of 
completeness, it is noted that in this case the test signals are not 
modulated by the transmission frequency f.sub.o since the passive 
intrusion detector 12, as is well known, does not have a transmitter or 
transmitting device. For certain circuit components, especially band-pass 
type arrangements, it can still be advantageous to nevertheless carry out 
a modulation whereby the transmission frequency f.sub.o is replaced by the 
corresponding mid-frequency. In a modified embodiment the passive 
intrusion detector 12 contains a modulating signal generator operating at 
a predetermined mid-frequency and modulating means connected in circuit in 
a manner corresponding to the transmission signal generator 4 and the 
mixer stage 95 in the active intrusion detector 10 shown in FIG. 1. 
The active intrusion detector 10 shown in FIG. 1 is also checked or tested 
for the correctness of the electrical parameters of its evaluation circuit 
5 at predetermined time intervals during its time of operation. The 
electrical parameters of the evaluation circuit 5 are, for example, 
amplification gain, mid-frequency, time constant, band-pass width, 
threshold values, sensitivity and so forth. FIG. 2 shows the time 
relationship of the tests or checks during such time of operation. For 
this purpose, the logic control circuit 8 contains means 8A for defining a 
sequence of operation periods t.sub.b having a predetermined duration in 
the range of about 10 sec to about 100 sec and periodically recurring test 
periods t.sub.i having a predetermined duration in the range of about 100 
ms to about 1,000 ms between individual operation periods t.sub.b. 
performed sequentially; then, the test signals generated by the test 
signal generator 90 are supplied to the corresponding locations at the 
evaluation circuit 5 within this test time t.sub.i during times t.sub.f 
ranging from about 40 to 400 ms. If only one test point is provided or in 
case the input occurs parallel at a number of test points in parallel, 
then there exists only one period t.sub.f as shown on the left-hand side 
of FIG. 2. This time period t.sub.f is selected such that disturbances 
which develop due to any switching states of the electronic components, 
cannot affect the test signals. During the so-called test clearing time 
t.sub.m, which is offset relative to the time period t.sub.f, the 
resultant signals are detected and evaluated in the logic control circuit 
8 via the lines or conductors 98 and the multiplex switch or multiplexer 
97. The time indicated in FIG. 2 are valid only with respect to the 
described exemplary embodiments relating to active and passive intrusion 
detectors. It will be appreciated that these times can be prolonged or 
shortened. It is also noted that the logic control circuit 8 shown in FIG. 
1 controls the times indicated in FIG. 2. 
FIG. 3 shows a frequency spectrum generated by the test signal generator 90 
due to the particularly simple test pulse shape of a single rectangular 
pulse. A modulation, if desired by the transmission frequency f.sub.o, 
merely has the effect of displacing the zero point (0) to the transmission 
frequency f.sub.o. This is symbolically indicated in FIG. 3. 
In FIG. 4 , a pulse train or series of pulses are plotted on the time 
abscissa t. The test signal generator 90 shown in FIG. 1 generates these 
pulse trains or series of pulses which are applied to the desired points 
or input locations of the evaluation circuit 5 by means of the switch or 
switching device 92 and the multiplex switch of multiplexer 96 during the 
time period t.sub.f of, for example, about 40 ms. In FIG. 4, each pulse 
has a time duration t.sub.p. 
FIGS. 5 and 6 show frequency spectra which originate from the pulse train 
shown in FIG. 4 when the time ratio of the pulse width or duration t.sub.p 
to the time t.sub.f changes over the total pulse train. The various 
frequency spectra are used for specific tests at special electronic 
components of the evaluation circuit 5. This will be further described 
hereinafter in connection with FIG. 7. FIG. 5 shows a frequency spectrum 
for the case that t.sub.f &gt;t.sub.p. The zero point (0) of this spectrum 
depicted on the frequency abscissa f is shifted to the transmission 
frequency f.sub.o when the test is made with the active intrusion detector 
10 containing the transmitter or transmitting device 4. The form of the 
spectrum shown in FIG. 5 is used for a point-selective measurement of 
electrical parameters in the evaluation circuit 5. 
The frequency spectrum shown in FIG. 6 and which is plotted on the 
frequency abscissa f results when the pulse train shown in FIG. 4 and 
which conventionally is generated by the test signal generator 90 is 
altered such that the time t.sub.f encompasses only some few periods of 
the pulse width or duration t.sub.p. Since this function is valid for a 
passive intrusion detector (without transmitter 4 and transmission 
frequency f.sub.o) as well as for an active intrusion detector (with 
transmitter 4 and transmission frequency f.sub.o), both these values are 
entered on the abscissa f. The form of the frequency spectrum shown in 
FIG. 6 is suitable for the integral testing of selective current circuits 
of the evaluation circuit 5. Particular considered in this respect are 
band-pass filters. 
To summarize, it can be said that the test signal generator 90 shown in 
FIG. 1 can generate frequency spectra of all possible types by alteration 
of pure pulse trains. Such frequency spectra are useful for the special 
testing purpose of specific current circuits in the evaluation circuit 5. 
FIG. 7 shows as a further exemplary embodiment an active ultrasonic 
intrusion detector 11. The evaluation circuit 5' contains an amplifier 54, 
a potentiometer 53, a modulator 55, band-passes 56 and integrators 57, 
comparators 58 as well as memories 59 with a following AND gate 60. The 
AND gate 60 generates an alarm signal 7 when output signals exist on both 
branches of the band-passes 56, the integrators 57, the comparators 58 and 
the memories 59 at the same time. Since the evaluation circuit 5' is not 
subject matter of the present invention, this evaluation circuit 5' will 
not be further described. 
The active ultrasonic intrusion detector 11 shown in FIG. 7 also has a 
transmitter or transmitting device 4 to which the transmission signal 
having the transmission frequency f.sub.o and generated by the 
transmission signal generator 94 is supplied via the closed switches or 
switching device 93 and 91. The transmission signal having the 
transmission frequency f.sub.o is fed via a line or conductor 61 to the 
modulator 55. In this modulator 55 the transmission frequency f.sub.o is 
used to demodulate the signal originating from the sensor or receiving 
device 1. During operation, the multiplex switches or multiplexers 96 and 
97 as well as the switch or switching device 92 are in the open state as 
shown in FIG. 7. In the exemplary embodiment shown in FIG. 7, the logic 
control circuit shown in FIG. 1 is constituted by contains a 
microprocessor 86 which controls the switches or switching device 91, 92, 
93 and the multiplex switches or multiplexers 96 and 97 via the control 
lines or conductors 81, 82, 83, 84 and 85. Furthermore, the microprocessor 
86 receives the resultant signals via an analog/digital converter 87 and 
evaluates these resultant signals. For example, the microprocessor 86 
carries out a comparison between the shapes of these resultant signals and 
the desired wave trains associated with the different check or test points 
of the evaluation circuit. 
In the following, there is explained first the so-called installation test 
and then the periodically recurrent operating test. 
When the alarm device of the active ultrasonic intrusion detector 11 is 
installed at the location at which the space 2 of the location is to be 
monitored, then it must be possible to adjust its responsive capability to 
its optimum value with respect to the space 2 to be monitored. This is 
effected by means of the microprocessor 86 which places the switch or 
switching device 91 via the control line or conductor 81 into the position 
alternate to the position shown in FIG. 7, so that the modulating means or 
modulator 95 is connected with the input of the multiplex switch or 
multiplexer 96. Furthermore, the switch or switching device 92 is placed 
via the control line or conductor 82 into the position alternate to the 
position shown in FIG. 7 so that the test signal generator 90 can apply 
its test function, shown in FIG. 4, to the modulator 95. If, now, the 
program in the microprocessor 86 determines that the test signals of the 
test signal generator 90 must be modulated by the transmission frequency 
f.sub.o of the transmission signal generator 94, the the switch or 
switching device 93 remains in the closed position as shown in FIG. 7. The 
modulation is carried out in the modulator 95. If the program in the 
microprocessor 86 determines that no modulation shall be done, the switch 
or switching device 93 is opened via the control line or conductor 83. In 
this case the pure test signals of the test signal generator 90 arrive at 
the multiplex switch or multiplexer 96 via the modulator 95. The 
microprocessor 86 adjusts according to its program the individual switch 
elements of the multiplex switch or multiplexer 96 via the control line or 
conductor 84. The resultant signals are taken-off or tapped-off, e.g. 
after the integrators 57, and are passed via the lines or conductors 98 to 
the multiplex switch or multiplexer 97. Since these signals are analog 
signals, they are converted in the subsequent analog/digital converter 87 
and fed as digital values into the microprocessor 86 which compares the 
resultant signals with the reference wave trains. As already mentioned in 
connection with FIGS. 3, 4, 5 and 6, the invention permits employing the 
most favorable frequency spectra as test signals for testing a wide 
variety of components. 
While there are shown and described present preferred embodiments of the 
invention, it is to be distinctly understood that the invention is not 
limited thereto, but may be otherwise variously embodied and practiced 
within the scope of the following claims. 
Accordingly,