| 摘要 |
<p>1,263,814. Signal amplitude analyser. WESTERN ELECTRIC CO. Inc. Oct. 27, 1969 [Oct.30, 1968], No.52465/69. Heading G1U. The amplitude of an A. C. signal received from signal oscillator 3 via a transmission path 1-2 under test is monitored by a "window" discriminator 30 which co-operates with bi-stable circuit 40 to produce a signal at a given frequency when the peak amplitude falls between two discriminator limits and zero signal or a higher frequency signal when it occurs respectively below or above the limits. A circuit 51, 52 tuned to the given frequency feeds an indicator circuit comprising transistor 55, relay 60 and indicator 64. The input signal is amplified 10 and applied via a protective circuit including diodes 12, 13 to the discriminator input. Switches 95, 97 select from voltage dividers 89-94 the bias voltages for setting the two limits of the discriminator and this provides an output signal when the input falls between the limits. Thus, it provides two output pulses for each cycle of input signal having a peak above the upper limit, a single pulse for each cycle of input signal having a peak within the limits and no output for a signal having a peak below the lower limit. The discriminator is coupled to a bi-stable circuit which switches when a negative going signal is applied and produces an output equal in frequency to the input signal when the amplitude of the input signal is high, at half the frequency of the signal when its amplitude is within the limits and no signal when its amplitude is low. The indicating circuit is tuned to accept the signals at half the frequency of the input signal. Time varying threshold signals for the discriminator can be provided by sources 102, 104.</p> |
