Abstract: A signal classifier performs measurements on an IF signal and determines from these measurements the nature of the modulation, if any, appearing on a received high frequency communications signal. The classifier distinguishes between double sideband AM, single sideband suppressed carrier voice AM, ASK, FSK, multi-channel FSK, unmodulated carrier and noise. The measurements include AM variation, the zero crossing rate in detected AM, the percentage of time the detected AM signal level exceeds a given amplitude, and wide and narrow band detected FM.

Abstract: An emergency roadside telephone system includes a plurality of self-powered, emergency telephone terminals positioned at remote locations, such as along roadways, to permit communication with a central station in order to obtain emergency assistance. Each emergency telephone terminal has a transmitter and a receiver for communication with the central station, a handset for providing voice communication and a plurality of emergency switches carrying symbols representative of various types of emergency assistance required such that a caller can request emergency assistance either by voice communication with an operator at the central station or, if there is a language barrier, by actuating the emergency switches.

Abstract: Pole-mounted equipment is adaptable for mounting on utility poles having a wide range of diameters and is relatively vandal-proof. A first equipment housing is secured to the pole by plural U-shaped bolts, the ends of which are tightly secured to the first assembly. Mounting brackets extend from the first assembly to a length greater than the largest pole diameter in said range and are secured to a second equipment housing. The brackets thereby define a uniform spacing between the first and second housings, irrespective of pole diameter. A front panel is secured to one of said housings and is protected by an access door. A cover, in the form of two generally L-section members, protects the housing from the elements and includes inwardly-projecting studs which extend into both housings where they are appropriately secured. Openings are provided in the top of the cover to accomodate the pole.

Abstract: Reliable cycle selection is achieved with LORAN-C pulses received under low signal-to-noise conditions. A tracking pulse is generated at the LORAN-C pulse repetition rate and is intended to be time-coincident with the end of the third 100 KHz carrier cycle in each received pulse. Sampling pulses are generated one-quarter and three quarters of a cycle before and after the tracking pulse and are used to sample a hard-limited, envelope-derived version of the received signal in which a phase reversal occurs at the start of the fourth carrier cycle. If the tracking pulse is coincident with the end of the third carrier cycle, a unique pattern of binary levels is sampled by the four sampling pulses. If the tracking pulse is too early or too late, corresponding early (left) and later (right) sampled level patterns result. Left and right occurrences of the tracking pulse are individually counted for a predetermined number of received LORAN-C pulses after which the difference between left and right counts is examined.