Abstract: In a hybrid fiber-coax distribution network, communications between a central station and particular end stations are encrypted using a working key (WK) of a symmetric encryption scheme. The central station has a public and private key (PPK) of a PPK encryption scheme, and some of the end stations can also each have a respective PPK. To provide secure communications for each end station, if the end station has a PPK, then the respective WK is generated in the central station and communicated, encrypted using the end station's public key (PK), to the end station. Otherwise, the WK is generated in the end station and communicated, encrypted using the central station's PK, to the central station. An individual identifier for each end station, and a cryptographic signature at least for end stations not having a PPK, can be communicated to the central station for authentication of the end stations.

Abstract: An intrusion detection electronic circuit package, includes a containment wall in combination with first and second transmission lines being organized in patterns spaced adjacent one another. Electronic circuitry, residing within the containment wall, includes a transmitter for transmitting signals in anti-phase relationship via the first and second transmission lines respectively. A receiver receives signals from the transmission lines and a detector connected to the receiver uses EXCLUSIVE OR logic to detect any significant in-phase components or interruptions in the signals received at the first and second inputs of the receiver. Disturbance of either transmission line in any attempt to breach the containment wall is likely to be detected.

Abstract: A muffler comprises two Helmholtz resonators, one tuned for high frequency and the other for low frequency. There is a resonance of the high frequency resonator volume's compliance and the effective tail pipe gas inertance which produces an undesirable low frequency noise. This is matched by the resonant frequency of the low frequency resonator, and suppressed thereby. A secondary effect to suppress noise at frequencies above said low frequency resonance due to the tailpipe gas inertance increasing linearly with frequency.

Abstract: A socket wrench device is provided as including a wrench handle having a drive head which circumferentially engages a socket having a plurality of circumferentially spaced side openings facilitating use in a minimum amount of vertical space. In an advantageous form of the invention, the drive head of the wrench handle includes a ratchet drive mechanism having a plurality of pawl fingers which engage corresponding side openings in the socket.

Abstract: A muffler of the Helmholtz resonator type has a housing surrounding a main gas flow conduit, the gas flow conduit having an apertured zone within the housing wherein apertures extend through the conduit wall, the shape of the conduit wall at the apertured zone being so varied that gas flows through the apertures into or out of the housing, the flow inhibiting the development of whistle noises.