摘要:
A pressure sensitive perimeter intrusion detector comprises at least two pressure sensitive housing members adapted for the transmission of acoustic waves in response to pressure applied to the exterior of the housing members. Each housing member is capable of providing a first electric signal in response to seismic waves or ground vibrations. In addition, distributed along the housing members are pressure-sensing elements for detecting pressure applied along the housing members. These pressure-sensing elements for each housing member provide a second electric signal having substantially no time delay. The first and second electric signals are transmitted to an evaluation circuit adapted to produce an alarm signal in response to the detection of an intrusion occurrence.
摘要:
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.
摘要:
In an ultrasonic alarm installation ultrasonic waves are continuously emitted into a monitored region and a frequency shift due to a moving object, e.g. an intruder, by virtue of the Doppler effect is evaluated for giving an alarm signal. The function control in this installation occurs during a test phase by means of brief aperiodic modulation of the emitted ultrasonic waves. The resulting brief frequency broadening generates in the same evaluating circuit a signal if the installation is functioning correctly. The time duration of the aperiodic modulation is selected to be so short that no standing waves can form, so that the function control can also work faultlessly if the installation, because of vectorial addition of the received ultrasonic waves, accidentally is in an insensitive state. Thus even coverings of the ultrasonic transmitter during a sabotage attempt can be recognized and distinguished from an insensitive state.
摘要:
In an ultrasonic alarm installation, ultrasonic waves are continuously emitted into a monitored region and a frequency shift caused by a moving object, e.g. an intruder, is received by an ultrasonic receiver and evaluated by virtue of the Doppler effect for generating an alarm signal. For testing the ultrasonic alarm installation the emitted ultrasonic waves are modulated by a plurality of modulation frequencies in the range of the frequency shifts effective for triggering the alarm signal. Thus, the function test can be carried out using the same electrical evaluation circuit as for generating the alarm signal. The plurality of modulation frequencies conjointly with the switch-off of the transmitter signal has the effect that the reflected signals, which arrive at the ultrasonic receiver with different phase relationships, are not vectorially added to the ultrasonic transmitter signal to yield zero, so that a reliable function control is always ensured. Furthermore and for determining changes in the monitored region, the time decay of the modulation-caused signal is compared with a reference signal in the electrical evaluation circuit after switch-off of the modulation signal.
摘要:
An infrared intrusion detector, utilizing as a sensor element a pyroelectric detector element, accomplishes evaluation of the output signal of the detector element with a charge amplifier, for instance by means of a capacitive feedback coupled operational amplifier, the output signal of which is reset at certain time intervals. The evaluation circuit operates independently of the detector capacitance and therefore enables optimum utilization of the pyroelectrical properties. By virtue of the short-circuit operation and the low ohmic properties of the circuit there is obtained a particularly good non-sensitivity against external disturbances and low noise and increased sensitivity.