U.S. Philips Corporation

Etat Francais

Etablissement Public De Diffusion De France

Bruce Murray

Peter R Brennand

Louis C Guillou

John C Beckley

Francoise M Coutrot

A pulse train divider circuit includes a first flip-flop (1) whose Q output is connected to the D input of a second flip-flop (2) whose Q output is connected to the D input of the first flip-flop (1). A pulse train to be divided is applied via an input (3) directly to the clock input C of the first flip-flop (1) and via a circuit (4) which delays the pulse train applied to the clock input C of the flip-flop (2) to provide a given phase relationship between the pulse trains at the two clock inputs. The circuit divides-by-two, and the resulting divided pulse trains available at the various outputs have phase relationships depending on the phase relationship of the applied pulse trains at the clock inputs.

Divider circuit

A system including a receiver which receives scrambled signals and subjects them to a descrambling process under the control of control words periodically conveyed to the receiver by a conditional access sub-system. A new control word is required for every 256 television frames constituting a descrambling period, which control word is transmitted during the preceding descrambling period. In order to reduce the time taken to initiate the descrambling process upon selection of a particular service or following an interruption therein, the initial control word then conveyed to the receiver is that for the 256 frame descrambling period following the existing descrambling period. The initial control word is followed by the control word for the existing descrambling period. Subsequent control words are successively conveyed to the receiver during the descrambling intervals preceding those to which such control words are respectively applicable.

Scrambled signal receiver

A receiver having an interface arrangement for connection between a television circuit and a conditional access sub-system conveys data via a bus having a four frame bus cycle period with a bit rate corresponding to the line rate. During a first part of the bus cycle period data is conveyed from the receiver to the sub-system sequentially as follows:

Receiver having an interface with a sub-system

An interface arrangement between a television receiver (1) and a conditional access sub-system (3), in particular for MAC type television signals comprises a bus having a first line (CKFH) conveying clock signals at television line frequency, a second line (DATA) conveying data during prescribed periods in a four television frame period bus cycle and a third line (DIRN) conveying a signal indicating the direction of data travel on the second line. The bus may be connected to a number of sub-systems (3(1), 3(2)) internal to the television receiver or may be connected via a connector unit (7) to external sub-systems (5(1), 5( 2)).

Interface between a receiver and a sub-system

In a receiver for a C-or D-MAC Packet television signal the bits of a pocket from the first subframe (DATA `A`) are multiplexed with the bits of a correspondingly positioned packet in the second subframe (DATA `B`) and applied to a data line of a packet bus so that the bits from the two packets alternate (DATA).

Method and apparatus for handling data in television signals

A receiver for recovering sound/data information for a number of services transmitted digitally as a packet multiplex has the data, after demodulation, applied to a first unit (3) where it is resynchronized for application to a sync and data extraction unit (19). In the extraction unit (19) the data packets are processed and applied, at a different clock rate, to a packet bus (25) to which a desired number of packet digital sound recovery devices (26) and packet encryption recovery devices (27) are connected. Instead of each recovery device (26, 27) interrogating all the packets of data those packets carrying a service identification address are processed in the extraction unit (19) and service addresses for user selected services are applied from a microcomputer (23) over an I.sup.2 C bus to the recovery devices (26, 27), control information also being received and interpreted by said extraction unit (19) and applied in similar manner to the recovery devices (26, 27).

Apparatus for receiving digital sound/data information

In television transmitter equipment for a television transmission system having a time multiplexed signal in component form, the vision components are derived from a vision source (1), encoded in a MAC encoder (2) and the encoded vision signals are modulated in a frequency modulator (3) which also receives oscillations from an oscillator (4). The modulated output of the frequency modulator (3) is applied through a multiplexer (5) to a transmitter (6) whose modulated carrier is applied to a dish aerial (7) for transmission to a satellite. The equipment contains a number of sources (8 to 15) of sound/data information which are separated into two groups, an `A` group of sources (8 to 11) and a `B` group of sources (12 to 15). Digital signals from the `A` group sources are applied to an `A` packet multiplexer (17) where the signals are assembled packet-by-packet into a given time area at a bit rate of 10.125 MHz. Corresponding signals from the `B` group sources are applied to a `B` packet multiplexer (18) where these signals are similarly assembled into a corresponding time area at the same bit rate. The outputs of the `A` and `B` packet multiplexers (17, 18) are applied to respective inputs of a further multiplexer (19) to produce within the time area bits derived from the two packet multiplexers. This data, the appropriate line sync words from a sync word generator (21) and data from a source (23) for lines 624 and 625 of each frame are assembled in a data assembler (20) to produce the data burst containing the sound/data components for the time multiplexed signal. This is modulated in a 2-4 PSK modulator (22) and the modulated output applied to a further input of the multiplexer (5). The data burst of the signal produced may be readily separated into its two groups to produce a data burst at the lower bit rate from one group for the transmission of a time multiplexed television signal over a medium of narrow bandwidth such as a cable channel.

Television transmission system

A wide-band frequency modulated DBS signal of the type having time sequential compressed chrominance and luminance (video) components is received by an aerial (1), frequency converted in a down converter (2) and applied to the input (4) of a conversion unit. The conversion unit has a tuner (5), i.f. stage (9,10) and a frequency demodulator (11) to produce baseband video which is applied after de-emphasis at (12) to a modulator (27) where the video is amplitude modulate onto a vision carrier from an oscillator (28). The modulated carrier is applied through a vestigial sideband filter (29) and an adder (30) to an output (31). Sound/data bursts present in the DBS signal are recovered in a stage (13) and processed in a processor (14) where the sound/data bursts are expanded to occupy approximately a line period at a bit rate which is an integral sub-multiple of the bit rate for the sound/data bursts in the received DBS signal. The expanded sound/data and clock frequency are digitally modulated in a modulator (32 ) onto a sound carrier from an oscillator (33), the modulated sound carrier being applied through a bandpass filter (34) and the adder (30) to the output (31). The output (31) is connected to a cable distribution system for which the narrow band signals produced by the conversion unit are suited as such systems cannot cope with high bit-rates. The processing of the sound/data bursts such that their bit rate is substantially reduced also simplifies the handling and demodulation processes for these bursts.

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Bruce Murray