Abstract: A scrambled frequency modulated video signal transmission system is provided with a headend station having a DC coupled amplitude demodulator for removing the amplitude modulation of a scrambled amplitude modulated baseband video signal. The low frequency components, e.g. 0-50 Hz, of the resulting scrambled baseband video signal are separated from the remaining high frequency components thereof for modulating a sub-carrier. The sub-carrier and the high frequency components are then combined and frequency modulated in a frequency modulator. The resulting scrambled frequency modulated video signal is then transmitted via fiber optic, coaxial and/or microwave transmission lines to a frequency demodulator in a hub station. In the hub station the output of a frequency demodulator is provided to a sub-carrier demodulator for producing the low frequency components, e.g. 0-50 Hz, which contain the scrambled sync pulse information.

Abstract: A toy helmet that permits the wearer to speak as to generate unintelligible noise so far as bystanders are concerned but which can be understood by another child wearing an identical helmet. Each helmet is equipped with internal and external microphones and an external speaker and internal earphones. Scrambler/descrambler circuitry is selectively connectable by means of a push-to-talk switch that delivers speech from the internal microphone to the external loudspeaker of the first helmet. The external microphone and the corresponding scambler/descrambler circuitry and push-to-talk switch of the second helmet delivers unscrambled speech to its internal earphone to permit the two helmet wearers to communicate intelligibly with one another. The scrambler/descrambler circuitry samples the low-pass filtered signals applied to its microphones at a sampling rate equal to the cut-off frequency of the low-pass filter.

Abstract: According to the invention, the control messages are constituted by a general addressing message (GCM), followed by shared addressing messages (SACM). The message (GCM) contains all the information common to all the user groups and a confirmation data item of the group of users and the messages (SACM) a shared address. Thus, the group is defined in a manner inherent in the control messages and can undergo reconfiguration at any time.Application to more particularly satellite broadcasting of television programmes.

Abstract: A method of operating a pay per view television system in which the television signal includes a program tag and an IPPV tag identifying memory locations in subscriber authorization memories. A subscriber can self-authorize his terminal decoder to unscramble a pay per view program with a password that inputs a "1" to the memory location identified by the IPPV tag. The program tag is changed to indicate the memory location identified by the IPPV tag, thus enabling subscribers who bought the program to unscramble the signal. The head-end periodically polls each subscriber terminal to determine the status of the second memory location and to reset it to "0" after the pay per view event.

Abstract: A surface acoustic wave (SAW) device and a related method, for providing improved frequency response characteristics from a SAW spectrum analyzer or channelizer. The device includes a spectrum analyzer with a preprocessing SAW device configured to provide output signals with narrower passbands, lower sidelobe components, or both. The preprocessing SAW device is a tapped delay line in one embodiment, to simulate positional offsets in the placement of input transducers of the analyzer. The tapped delay line can also be used to provide amplitude weighting or can be configured in a chirp spacing, to transform the spectrum analyzer into a chirp analyzer. Another embodiment employs a thinned-electrode prefilter as the preprocessing device, to yield a frequency response with multiple narrow passbands, which are used to narrow the individual channel passbands of the spectrum analyzer or to suppress sidelobes in the frequency response.

Abstract: Cryptographic methods and apparatus for forming, checking, blinding, and unblinding of undeniable signatures are disclosed. The validity of such signatures is based on public keys and they are formed by a signing party with access to a corresponding private key, much as with public key digital signatures. A difference is that whereas public key digital signatures can be checked by anyone using the corresponding public key, the validity of undeniable signatures is in general checked by a protocol conducted between a checking party and the signing party. During such a protocol, the signing party may improperly try to deny the validity of a valid signature, but the checking party will be able to detect this with substantially high probability. In case the signing party is not improperly performing the protocol, the checking party is further able to determine with high probability whether or not the signature validly corresponds to the intended message and public key.

Abstract: The present invention provides a novel dynamic vertical height control circuit for a CRT display which is adapted to receive an input signal over a broad range of variable frequencies. The dynamic variable input frequency is applied to a free running oscillator which is coupled to a ramp generator for producing a ramp output signal. The ramp output signal is coupled back through novel feedback means comprising a comparator and means for determining the magnitude of the ramp output signal voltage for producing a feedback signal which is applied as a control signal to the ramp generator. The feedback control maintains a vertical height control signal which maintains a constant vertical display size on the CRT display.

Abstract: A data locking system which modifies data in accordance with a renewable key variable derived from the exclusive ORing of a pseudorandom combination number from an external source means with an altered key variable.

Abstract: Rodents are driven off and kept away from burrows in a subterranean area by driving cylindrical housing containing respective shock wave generators into the ground. The shock wave generators are each designed to produce at timed intervals, damped vibrations which radiate into the surrounding ground.

Abstract: The protection of the transfer of data between a videotex terminal (TVX) and a server (SE) is carried out by means of an additional package (BA) connected to a video adaptor connector (PPI) of the terminal (TVX). In a presession embodiment, the package acts on the switching device (AIG) of the terminal by monitoring any other action on said switching equipment. The switching cabinet and the server conduct dialogue according to a predetermined sequence of operations comprising the definition of a transmitted session key encrypted in accordance with a basic key. Any anomaly occuring during this dialogue aborts the presession mode.

Abstract: The invention is an apparatus and method for validating that key management functions requested for a cryptographic key by the program have been authorized by the originator of the key. The invention includes a cryptographic facility characterized by a secure boundary through which passes an input path for receiving the cryptographic service requests, cryptographic keys and their associated control vectors, and an output path for providing responses thereto. There can be included within the boundary a cryptographic instruction storage coupled to the input path, a control vector checking unit and a cryptographic processing unit coupled to the instruction storage, and a master key storage coupled to the processing means, for providing a secure location for executing key management functions in response to the received service requests. The cryptographic instruction storage receives over the input path a cryptographic service request for performing a key management function on a cryptographic key.

Abstract: Different digital radio transceiver front panel escutcheon plate modules are provided for different optional transceiver configurations. A security circuit is provided in each module in addition to user controls and associated circuitry. The security circuit is connected to communicate serial data signals to and from a digital signal controller which is part of the main transceiver circuitry. The controller is capable of performing any of various basic and option functions under control of program control instructions stored in an associated non-volatile memory. Upon initial application of power to the transceiver, the controller transmits a sequence of digital signals to the security circuit. The security circuit permutes the sequence of signals into a different sequence, the specific permutation used being arbitrarily complex--and dependent on transceiver "option" features to be enabled. The security circuit communicates the permuted signal sequence back to the controller.

Abstract: A temperature stable television signal trap filter device is easily produced in a wide range of temperature compensating values using commercially available components for securing pay television systems. The trap filter has a series pole and a shunt pole capacitively coupled to the series pole. A first parallel capacitor circuit having a total capacitance and a total temperature compensating value forms a capacitive part of the series pole and a second parallel capacitor circuit forms a part of the shunt pole. Both the first and second parallel capacitor circuit include a first standard capacitor having a first standard temperature compensating value coupled in series with a first branch of the parallel capacitor circuit and a second standard capacitor having a second standard temperature compensating value coupled in series with a second branch of the parallel capacitor circuit.

Abstract: In a pay television system, a program signal is transmitted scrambled to prevent its unauthorized reception, the scrambled signal being accompanied by authorization codes, one for each authorized subscriber, a subscription key and a pay-per-view key. At a receiver, if the appropriate authorization code is received, the receiver functions in the subscription mode in which mode the subscription key provides for the descrambling of the program signal. If the appropriate authorization code is not received, indicating that the subscriber is not pre-authorized to receive the program in an intelligible manner, the receiver is set to function in a pay-per-view mode in which mode, on request, the pay-per-view key provides for the descrambling of the program signal. If there is a delay receiving the appropriate authorization code, the receiver can be set into the pay-per-view mode for at least the period of the delay, so that the scrambled signal is immediately rendered intelligible.

Abstract: A license management system which includes a license management facility that determines whether usage of a licensed program is within the scope of the license. The license management system maintains a license unit value for each licensed program and a pointer to a table identifying an allocation unit value associated with each use of the licensed program. In response to a request to use a licensed program, the license management system respond with an indication as to whether the license unit value exceeds the allocation unit value associated with the use. Upon receiving the response, the operation of the licensed program depends upon policies established by the licensor.

Abstract: A cable television channel security system for installation at a subscriber location to control access to one of more channels of RF signals transmitted from a headend location via conventional cable means. The system is divided into two major subassemblies, a so-called address module and a switch module, the latter including one or more conventional traps. The address module receives a sequence of coded signals selectively inserted through a personal computer at the cable system business office and carried on portions of the RF signals transmitted at the headend. The coded signals include a first portion unique to each subscriber location and a second portion indicating which of the premium channels are to be directed to traps, and which are to bypass the traps of the switch module. As signals are transmitted and received in the clear, i.e.

Abstract: On-board satellite switching is performed in three stages, an outer stage of switching on the up-link side for routing the received signals to either demodulators or frequency translators, a first inner stage of switching, preferably a baseband switch and processor, for routing and processing the outputs of the demodulators, a second inner stage of switching, e.g., a microwave switch matrix, for routing the outputs of the frequency translators, and an outer stage on the down-link side for assembling and routing the down-link spot beams. For a multiple hopping-beam system, the outer stages are microwave switch matrices, and for a hybrid scanning-hopping system the outer stages are beam forming matrices. A general purpose modified rearrangeable switch matrix is also disclosed.

Abstract: A method insures the NETBIOS names are not illegally used on a local area network. The NETBIOS protocols use a naming system that allows any station to claim a name or set of names that are not already in use. This potentially allows any user to "masquerade" as another user, or service machine, by claiming the name when the real user is not connected to the network. This method detects these attempted masquerades, disconnects the offending station from the network, and logs information about the attempt.

Abstract: A descrambler for a scrambled channel having a suppressed horizontal synchronization pulse which scrambled channel is provided in a broadband cable television signal along with nonscrambled channels. A signal splitter receives the broadband CATV signal and provides first and second split outputs. A switch coupled to the second output of the signal splitter passes the horizontal synchronization pulse of the scrambled channel and blocks the video signal of the scrambled channel. The horizontal synchronization pulse passing through the switch is then phase adjusted to synchronize with the horizontal synchronization pulse of the scrambled channel provided at the first output of the signal splitter, and both horizontal synchronization pulses are summed in a combiner along with the video/audio signal provided at the first output of the signal splitter. Consequently, the full synchronization pulse is provided at the output of the combiner to descramble the scrambled channel.

Abstract: An ultrasonic ranging and data telemetry system determines a surveyor's position and automatically links it with other simultaneously taken survey data. An ultrasonic and radio frequency (rf) transmitter are carried by the surveyor in a backpack. The surveyor's position is determined by calculations that use the measured transmission times of an airborne ultrasonic pulse transmitted from the backpack to two or more prepositioned ultrasonic transceivers. Once a second, rf communications are used both to synchronize the ultrasonic pulse transmission-time measurements and to transmit other simultaneously taken survey data. The rf communications are interpreted by a portable receiver and microcomputer which are brought to the property site. A video display attached to the computer provides real-time visual monitoring of the survey progress and site coverage.