Abstract: The effective sensor width of a path following vehicle guidance system is enlarged by having a first gain control amplifier for amplifying the sum of the path sensor signals, a second gain control amplifier for amplifying the difference of the path sensor signals and a third amplifier, in tandem with the second amplifier for amplifying the output of the second amplifier once the second amplifier's output has peaked out. All three amplifiers are gain-controlled by the same negative feedback signal. The outputs of the first and third amplifiers are synchronously detected to provide an error signal for an electromechanical steering servo for the vehicle.

Abstract: A telephone network protective coupler for connecting terminal equipment to a telephone central office by means of a telephone line. The coupler includes two hybrid circuits which are interconnected to form a transmitting path and a receiving path. A power limiter in the transmitting path can be programmed remotely by selection of an external programming resistor without the direct introduction of noise into the transmitting path. The programming feature permits the gain of the transmitting portion of the device to be varied in steps from 0 to -12dB., and the maximum power output to be varied correspondingly in steps from 0 to -12 dBm. in order to arrive at an optimum signal power level of -12dBm. at the central office. The power limiter includes a controller gain amplifier for varying the attenuation of the transmitting path to a.c. signals, a remotely adjustable attenuator connected to a d.c.

Abstract: In a radio receiver IF amplifier, a high gain AGC circuit produces a constant signal output regardless of input signal levels in excess of a threshold value. A summing amplifier responds to the AGC voltage and the IF amplifier current to develop a d - c potential directly proportional to the signal input to the amplifier both above and below the AGC threshold. This voltage is useful in the squelch and signal strength meter circuits.

Abstract: In an environment of acoustic noise, such as a car radio playing in traffic or engine noise, both the volume (AGC) and dynamic range (Compression) of the audio amplifier are controlled by a local ambient acoustic noise sensor, such that gain is increased and dynamic range decreased simultaneously with increased ambient noise.

Abstract: A receiver with an automatic gain control system is disclosed in which the signal path between the output coil of an antenna tuning coil and a first stage of a circuit supplied with a received signal from the antenna tuning coil is connected in parallel with a plurality of variable impedance elements, resistors are connected in series between at least the plurality of variable impedance elements, and an automatic gain control signal is supplied to the plurality of variable impedance elements to thereby perform an automatic gain control.

Abstract: A fast-attack circuit is employed in an A.C. amplifier automatic gain control circuit to temporarily apply a D.C. gain control signal immediately to the amplifier circuit in response to a sudden signal increase in excess of a predetermined threshold level to avoid the problems of over-attack and pinch-down which might otherwise arise during the period required for the AGC loop to achieve stabilized control following the inception of the signal increase.

Abstract: A demand cardiac pacemaker is disclosed as comprising an input sensing circuit portion of improved sensitivity to heart beat signals of relatively low amplitude. In particular, the input circuit portion includes a first sensing, bipolar transistor biased by a GaAsP light-emitting diode (LED), and a second amplifying, bipolar transistor whose base is coupled to the collector of the first transistor. Further, the output of the second transistor as taken from its collector is fed back through a suitable shaping circuit to the emitter of the first transistor, whereby controlled high gain and desired frequency/amplitude discrimination characteristics are achieved from the first and second transistors, so that the input sensing portion of the pacemaker circuit is responsive to heart signals above a predetermined level without sacrificing gain.

Abstract: A bistatic velocity detector system for underwater detection of objects of redetermined magnitude wherein the water may be capable of continual variations in velocity. The system includes a compensator that has an automatic gain controlled amplifier whose controlled output signal is applied first to an a.c./d.c. converter and then to an integrator circuit. A first voltage comparator receives the integrated signal to drive a relay for activating an alarm when a threshold is exceeded. A second voltage comparator having a lower reference voltage applied thereto drives an RC timer circuit whose output signal is applied to the gate of a field effect transistor of variable impedance for varying the gain of the operational amplifier. An alternative embodiment includes a dual gate transistor for use in the gain controlled amplification of the loop.