Abstract: A time divided digital signal transmission system includes a transmitter for converting plural analog signals to digit signals, generating multiplexed time divided signals from the digital signals, and transmitting the multiplexed time divided signals by a digital data transmission circuit. The system further includes a receiver for receiving the multiplexed time divided signals, demultiplexing the multiplexed time divided signals so as to thereby obtain the original digital signals and converting the original digital signals back into the original analog signals. The system is arranged to effectively utilize both synchronizing signals and clock signals for the analog to digital conversion and the digital to analog conversion in the system.

Abstract: An FSK data transceiver for long distance data communication is arranged such that transmitted data is composed of coded information in binary form. The data carrier signal utilized in the transceiver is a continuous rather than an intermittent signal and the receiver portion of the transceiver tracks the transmitted carrier signal so as to not lose the signal. The receiver performs an averaging process on the received data for improving the signal to noise ratio of the received signal.

Abstract: A delta modulation system which has a reduced quantization noise level. The system compares its input signal with an integrated and filtered version thereof and inhibits the integration when the difference therebetween has not varied for two or more consecutive clock periods.

Abstract: This invention provides an elastic surface wave device utilizing Bluestein-Gulyaev wave and constructed by a unitary body of a piezoelectric plate having a plurality of transducers thereon, wherein the wave propagation surface being coated with an insulating rubber and being embedded in molding by an insulating powdered epoxy resin, or whose body is attached on a unitary supporting substrate via double adhesive layers; wherein one layer is composed of one kind of adhesive resin and the other is composed of another kind of adhesive resin different from the former in ultrasonic property. This device is advantageous because it has a low spurious signal level without increasing insertion loss, and is easy to manufacture and inexpensive. This invention also provides an effective method for making the device.

Abstract: A piezoelectric transducer is secured to the surface of a glass sheet to translate mechanical vibrations generated in the glass sheet into an electrical signal when a crack is produced. A detection circuit is connected to the transducer to determine whether the frequency of the signal is above or below a predetermined value. If the frequency is higher than the predetermined value, a warning signal is derived to indicate a crack and therefore probably a burglary. Alternatively, the piezoelectric transducer in the transmit mode is excited electrically by an impulse to introduce an elastic wave into the glass sheet. A gate circuit is connected to the transducer to pass signals resulting from reflection of the elastic wave from discontinuities in the glass sheet which result from a crack. The reflected crack indicating signals are passed through the gate to the transducer when it is in the receive mode.