Abstract: A test circuit that is particularly suitable for inclusion on an LSI chip when testing a new technology. The circuit will enable accurate determination of the turn-on and turn-off delays of a logic circuit on the chip. Two related feedback loops are provided, one of the loops containing the circuit being tested. The differences in time duration between related portions of the two loops correspond to the turn-on and turn-off delays of the circuit being tested.

Abstract: A signal generator having a digital temperature compensation circuit contains high and low frequency quartz oscillators (HF and NF), the low frequency oscillator being used for temperature compensation. Both oscillators are manufactured such that the descending portion of the temperature dependent parabolic frequency curve of the low frequency oscillator passes through the temperature inversion point of the parabola of the high frequency oscillator.The frequencies of both oscillators are first adjusted such that the ratio thereof is inversely proportional to the ratio of the parabolic temperature coefficient, i.e., f.sub.1 :f.sub.2 =.beta..sub.2 :.beta..sub.1. Subsequently two substantially identical reference frequencies are adjusted and, by feeding back the output frequency, combined in such a manner that an output frequency independent of temperature is produced which is determined substantially by the high frequency oscillator.

Abstract: A signal generator includes a high frequency oscillator such as a quartz crystal oscillator at a frequency of 4.19 MHz, a low frequency quartz oscillator with a frequency of 32 kHz, a beat frequency generator for producing a correction signal which is transmitted to a programmable frequency divider, and an electronic switch for periodic switching of the high frequency quartz oscillator. By periodically switching-on the high frequency quartz oscillator, comparing its frequency curve with that of the low frequency quartz oscillator and and appropriately adjusting the programmable frequency divider, the advantages of long term stability, temperature of behavior and aging of a high frequency oscillator are combined with the low current consumption characteristics associated with the low frequency quartz oscillator, whereby the life of a battery powering the signal generator can be substantially extended.

Abstract: A low frequency modulating signal and a high frequency carrier signal circuit employing a twin-T oscillator having an integrated circuit operational amplifier for producing the modulating signal and an L-C resonant feedback oscillator having a transistor amplifier for producing the carrier signal, and a monitoring shunt regulator for supplying a reference potential to the twin-T oscillator and biasing and operating potentials to the L-C resonant feedback oscillator and for deactivating the L-C resonant feedback oscillator when an increase in resistance occurs in the shunt regulator.

Abstract: An electronic timing system for controlling a plurality of electrically controlled watering valves comprising a free running multivibrator circuit having a plurality of individually adjustable resistor-capacitor circuits for controlling the frequency. A divide-by-N counter, when filled, controls a stepping counter for successively activating different ones of the valves and, in turn, selects different ones of the resistor-capacitor circuits to control the time each of the valves is activated. Operation of the multivibrator circuit is initiated by a clock operated day-of-the-week counter having pre-settable switch means for enabling or disabling operation of the multivibrator circuit during any selected day. A repeat cycling control device is provided to selectively cause repeated cycling for different numbers of times and a delay device is provided to delay repeat cycling for different time periods.