Telex Communications, Inc.

Robert Boschgmbh

Robert B Basine

Keith Jenkins

LaRhue G Friesen

Charles E Conner

A switchable band-pass filter is described that includes a first capacitor, a first switch circuit, and a second switching circuit arranged in parallel between a first node and a second node. The first switching circuit includes a third node and a first switch. The first switch is coupled between the third node and the second node. The second switching circuit includes a fourth node and a second switch. The second switch is coupled between the fourth node and the second node. A linking circuit is coupled between the third node. Methods for operating the switchable band-pass filter are also described.

Switched band-pass filter

To transmit encoded information such as for example voice messages between remote transceivers, a transmitter digitizes and encodes an audio signal and then transmits the resulting digital coded signal to the receiver. The receiver decodes the signal and converts it back to an audio signal. The received encoded digital signal is used to reset the timing clock in the receiver so that the timing is synchronized in the receiver and transmitter by the transmitted encoded information. The encoder transmits digital information to a shift register. Encoding switches select certain stages of the shift register and the transmitter transmits the exclusive-OR of the digitized message and the output of the selected stages. This signal is also the input to the shift register. The information transmitted to the receiver is a scrambled digital signal. In the receiver, the coded information synchronizes a clock for the shift register from the encoded digital signal that it receives and selects the stages of the shift register that unscramble the coded information for conversion to an audio signal suitable for the speaker.

Synchronization technique and method and apparatus for transmitting and receiving coded signals

An inexepensive diversity receiver compares the received signal strength signal with a threshold value. When the received signal falls below the threshold value a signal is transmitted through a conductor and a delay circuit to a NAND gate. If the signal is applied to the the two inputs of the NAND gate at the same time, the output of the NAND gate switches a bistable flip-flop which in turn connects or disconnects a second antenna that is 180 degrees in phase from the first antenna between a state in which the signals from the two antenna is combined and a state in which they are not combined and only one antenna applies signals to the receiver.

Growing community of inventors

Waverly, NE, United States of America

Robert B Basine