Abstract: A vehicle anti-theft system includes programming vehicle identification numbers or a corresponding identifier value into a read-only memory portion of each computer on board the vehicle. The computers are all linked through a multiplex communication system that has a monitoring port. The monitoring port facilitates coupling an external device to the multiplex communication link. The external monitoring device is used to determine the contents of the read only memory portion on each component to determine whether any of the components were stolen from another vehicle, for example.

Abstract: An anti-theft system includes a strategy for providing secure communications between a system controller and a remote signaling device. A communications initiator allows the transfer of information or signals between the system controlling and the remote signaling device only under pre-defined conditions. The system controller preferably includes a transmitter portion for transmitting signals or information to the remote device and a receiver portion for receiving signals from the remote device. Similarly, the remote device preferably includes a transceiver so that two-way communication is accomplished between the controller and the remote signalling device.

Abstract: A security system that is useful for protecting vehicles from theft and buildings from unauthorized entry, for example, includes utilizing random numbers within remotely transmitted signals. A remote signaling device transmits a signal to a system controller with instructions for a desired operation of the system. The invention prevents a potential thief from capturing one or more transmitted signals and later mimicking or predicting a subsequent signal by including or utilizing a random number when generating the transmitted signal. The random number is incorporated into the transmitted signal in one of several ways according to this invention. Single-use or limited re-use of random numbers enhances the security and integrity of the system.

Abstract: A vehicle security system combines anti-driveaway protection with vehicle entry signalling. Either a remote signalling device is used to generate a remote signal or an input device, mounted on the vehicle, is used to generate an access signal. An entry control unit receives and interprets the remote signal or the access signal and unlocks the vehicle doors when appropriate. At the same time, the entry control unit communicates with an engine controller that an appropriate signal has been received. In response, the engine controller enables the vehicle engine to be started so that the vehicle can be driven in a conventional manner.

Abstract: A SAW detector has a SAW transducer 10 disposed on the surface of a piezoelectric substrate 12 which injects a SAW 20 in response to an RF input signal applied to line 14. A semiconductor charge transport region 30 comprising a charge transport channel 32 sandwiched between two charge confinement layers 34,36, is disposed above the substrate. A source electrode 40 provides electrons to the channel 32 and a drain electrode 42 removes electrons from the channel 32. The electric fields generated by the SAW 20 travel along the channel 32 and provide a forcing function to move the electrons from the source electrode to the drain electrode as a continuum, not in charge packets, thereby providing output current 48 on a line 49 indicative of the SAW 20 frequency.

Abstract: An acoustic charge transport device having a number of signal tap electrodes has revealed unexpected insensitivity to electrode spacing and unexpected sensitivity to electrode width. Spacing of one-half SAW wavelength between consecutive electrodes and an electrode width of .lambda./20 are preferred for low frequency response.

Abstract: A simplified heterostructure charge transport device has a GaAs transport layer that is the top layer of the device, deposited on an (Al,Ga) As barrier layer for vertical confinement of charge packets. Confinement at the top surface is provided by pinning of the conduction band surface states.