Abstract: A system for transmitting digital programming includes a program source providing digital information, circuitry for modulating the digital information onto a visual carrier modulated with analog television programming, and a visual transmitter coupled to the modulating circuitry. Using a phase modulation method, the system phase modulates the digital information onto a visual carrier, reduces the baseband frequencies of the phase modulated visual carrier, and amplitude modulates the phase-modulated video carrier onto a video signal. The amplified and encoded video signal are combined with an amplified sound signal and transmitted. Using an additive method, the system modulates the sidebands of the video carrier with the digital information and amplitude modulates the video signal onto the video carrier. The data-modulated sidebands are phase-shifted such that they will be in quadrature with the amplitude-modulated video signal.

Abstract: A system for transmitting digital programming includes a program source providing digital information, circuitry for modulating the digital information onto a visual carrier modulated with analog television programming, and a visual transmitter coupled to the modulating circuitry. Using a phase modulation method, the system phase modulates the digital information onto a visual carrier, reduces the baseband frequencies of the phase modulated visual carrier, and amplitude modulates the phase-modulated video carrier onto a video signal. The amplified and encoded video signal are combined with an amplified sound signal and transmitted. Using an additive method, the system modulates the sidebands of the video carrier with the digital information and amplitude modulates the video signal onto the video carrier. The data-modulated sidebands are phase-shifted such that they will be in quadrature with the amplitude-modulated video signal.

Abstract: A system for transmitting digital programming includes a program source providing digital information, circuitry for modulating the digital information onto a visual carrier modulated with analog television programming, and a visual transmitter coupled to the modulating circuitry. Using a phase modulation method, the system phase modulates the digital information onto a visual carrier, reduces the baseband frequencies of the phase modulated visual carrier, and amplitude modulates the phase-modulated video carrier onto a video signal. The amplified and encoded video signal are combined with an amplified sound signal and transmitted. Using an additive method, the system modulates the sidebands of the video carrier with the digital information and amplitude modulates the video signal onto the video carrier. The data-modulated sidebands are phase-shifted such that they will be in quadrature with the amplitude-modulated video signal.

Abstract: A method for calibrating a remote pilot unit is provided wherein both the pilot receiver and the pilot transmitter are calibrated. A test signal of a known magnitude is applied to the pilot unit and the magnitude actually received by the pilot receiver is determined. The two magnitudes are compared and a correction signal is determined. To calibrate the remote transmitter, a signal of a nominal magnitude from the transmitter is applied to a measurement device and the determination is made by the measurement device of the actual magnitude applied. The actual magnitude and the nominal magnitude are compared and a transmitter correction signal is determined. The receiver correction signal and the transmitter correction signal are stored in permanent memory within the pilot unit. This process is repeated at a plurality of frequencies to provide a signature for both the transmitter and the receiver.

Abstract: An expandable, multipurpose digital and analog communications system in which a plurality of remote interrogator units connected in a branch of the system are isolated from one another by band stop filters to permit simultaneous polling without interference with other operations. Also disclosed is a premium service control unit which makes uses of a frequency agile oscillator.

Abstract: An eddy current coupled transducer and external electrical circuit are disclosed for use with a fluid actuator for detecting the relative position of the reciprocating member of the actuator. The transducer includes a fitting providing a fluid pressure seal whereby the transducer can be fitted to the actuator and communicate with its interior. The transducer detects the absolute position of the reciprocating member of the actuator by eddy current coupling. A change in the amplitude of the high frequency signal supplied to the transducer by the external electrical circuit occurs when the reciprocating member is in close proximity to the transducer. This change in amplitude is detected by the electrical circuit to provide an on-off switching signal for associated equipment in response to the position of the actuator reciprocating member.

Abstract: A communication system in which individual stations are connected to a control center by a transmission medium common to all of the stations to allow the transmission medium common to all of the stations to allow the transmission of messages in the form of digital signals between the control center and the individual stations. The length of a message transmitted to or from a specific station is determined by the information content of that message and is independent of the length of other messages to or from the same station or other stations. In particular, the invention relates to stations for use in such a system, and especially to means provided in each station to allow modular expansion units to be connected directly to the station or to another modular expansion unit that is connected, directly or indirectly, to the station.

Abstract: A full duplex data modem for general application, e.g., cable system signal distribution, terrestrial or satellite radio link, or the like includes transmit and receive portions for permitting reliable communications between plural stations coupled to the common communications link.In accordance with the present invention, a fixed value is applied to a modem adapted in a test mode to speak with itself, and the number of transitions counted at the modem receiver output, to measure the error rate of an entire system.

Abstract: A system including a data modem having transmitter and receiver sections. The modem transmitter includes a multi-level data encoding system, a stable carrier generator and a selected transmission frequency, and a double sideband suppressed carrier modulator to modulate the multi-level signals on the carrier. All filtering to shape the signals in the transmitter section is done prior to modulation and, in the receiver section, after demodulation. Signals from several modem transmitters, each occupying its own assigned band, are multiplexed with two pilot carriers spaced by a predetermined frequency difference. The modem receiver includes a circuit to separate one of the carriers from the received band and mix that carrier with signals in a limited part of the band to shift the frequency of signals in the limited part of the band to an intermediate frequency (IF) band. A desired signal can be selected by frequency-shifting the IF signals so that the carrier frequency of the desired signal is at zero.

Abstract: Frequency response of a signal path over which frequency-spaced signals are transmitted is analyzed by sweeping relatively narrow pass band tunable receiving means across the frequency band expected to be received at the location to be analyzed. Incoming signal to which the tunable receiving means is tuned at any instant is used to control the frequency of a voltage controlled oscillator. The frequency of oscillations produced by the oscillator has a known relationship to the amplitude of the instantaneously received signals, and these oscillations are transmitted to a frequency-to-amplitude converter at a measuring location. The converter produces an output signal that has an amplitude which is a function of the frequency of oscillations applied to it. A spectrum indicator at the measuring location is connected to the converter to produce a visual display of the amplitude of signals received at the location at which the characteristics of the transmission path are being analyzed.

Abstract: A method and system for scrambling amplitude-modulated or frequency-modulated signals at a transmitter and descrambling the scrambled signals at a receiver. The scrambling is effected at the transmitter by shifting the phase of only the carrier component of the modulated signal by from 80 to 100 carrier degrees, preferably exactly 90 carrier degrees, the phase shift either advancing or retarding the carrier component out of its proper phase relationship with the side band components of the modulated signal in the transmitted version of the modulated signal. The descrambling of the transmitted version of the modulated signal is effected in a receiver, prior to demodulation therein, by restoring the carrier component back into its proper phase relationship with te side band components of the modulated signal.