Independent Broadcasting Authority

Peter Richard Hutt

Philip John Dodds

Alan Ronald Blake

Gunter Von Cavallar

Brian Neil Douglas

Arthur G Mason

Andrew Dean

Test apparatus for monitoring transmissions contained in a broad band television video signal is disclosed including a sampling device operating at an integer multiple of the digital bit rate which is above the Nyguist level and a temporary storage device for storing the sample produced by the sampling device. A microprocessor is used to compute from the stored samples a value of a parameter of the digital transmission and to control the sampling device whereby the sample can be taken at appropriate points for the parameter to be tested. To that end, conversion means are provided for converting the stored samples so as to recreate the input digital transmission for resampling at the points determined by the microprocessor.

Test apparatus for monitoring digital transmissions

Apparatus is disclosed for producing a test signal having a predetermined amount of distortion, including a first pulse generator (11) for producing a plurality of first pulses, a distortion pulse generator (18, 21) for producing a plurality of distortion pulses, and an adder circuit for adding the first and distortion pulses to produce a composite signal having a main portion of amplitude and shape identical to the first pulse and to which is added at least one of the distortion pulses.

Digital testing apparatus

According to the invention, a television receiver system comprises selector equipment for selecting information in the form of coded characters, received separately from any picture signals, from a single information channel or a small number of information channels and routing the selected information to a storage device, and a reading device operable, when actuated, to read the information from the storage device repeatedly and feed it, via a character generator, for display by an intensity modulated raster.

Television receiver system having facility for storage and display of

In any television transmission system there are periods during which the wide-band picture signals are absent. The invention provides a signal generator system for the transmission of digital information representing a series of pages of alphanumeric or graphical symbols piecewise during these periods. At least one peripheral generating device is provided for supplying digitized data to a main storage device (conveniently of the magnetic disc type) and transfer means is operable to read out portions of the data from the main storage device and store them temporarily in a second storage device. Discharge means is operable to discharge portions of the data from the second storage device at intervals to provide output signals for insertion in a television signal during periods as aforesaid.

System for processing data signals for insertion in television signals

Apparatus for processing groups of digital data for transmission comprises a run-in signal generator for providing at the output of the apparatus an output in which the groups of data are each preceded by a run-in signal, said apparatus being so constituted that the output is in the form of digital signals of the complemented type, and a start code generator operable to provide a start code with at least one break of complementation and arranged to insert a start code between each group and its preceding run-in signal. The apparatus is especially suitable for the transmission of data intermittently, e.g. during periods of a television signal unoccupied by wide-band picture signals. Because of the complementation break, the start code cannot arise from a data combination. Good reliability of reception is achieved on channels susceptible to interference. An apparatus for reception comprises a memory device controlled by a clock circuit responsive to the run-in signal, and means responsive to the start code to route the data for display purposes.

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Richmond, United Kingdom

Peter Richard Hutt