Compagnie Industrielle Des Telecommunications Cit-Alcatel

Alcatel

Jean-Claude Lacroix

Gerard Bourret

Jacques Pochet

Pierre Franco

Stephane Le Gall

A method of transmitting signalling along a bidirectional digital transmission link consists in transmitting from an intermediate equipment of the link a signalling message in two parts. One is a characterizing part the form of which depends on the signalling type and which is substituted for data of one of the digital bit streams carried by the link in the direction from one of the terminals referred to as the processing terminal. The other is a localizing part whose form is independent of the signalling type and which is substituted for data of the digital bit stream carried by the link in the direction towards the other, so-called relay terminal. The relay terminal responds by sending an acknowledgement message to the processing terminal, the time-delay of this relative to the characterizing part being used to identify the sending equipment. A signalling message transmission circuit controls switching circuits inserted into the paths of the digital bit streams carried by the link. The equipment for transmitting signalling along a bidirectional digital transmission link comprises a clock circuit defining in terms of the period of its output signal the duration of a signalling message characterizing part. Its half-period defines the duration of a localizing part. There is also a circuit for selecting the first complete period of the clock circuit output signal after a signalling transmission request, as well as circuits for composing the two parts of the message.

Signalling method and device for bidirectional digital transmission link

Apparatus for implementing a remote signalling method which consists in momentarily replacing the transmitted digital data stream by a remote signalling message which is built up from not more than n identical and nonconsecutive sequences of N bits, with the first sequence of each message being present on each occasion that a message is sent, and with the remaining n-1 sequences of each message representing, by their presence or absence, the values 0 or 1 of n-1 digits in a binary number encoding remote signalling data. FIG. 2 shows a circuit for transmitting a remote signalling message from an equipment along a very high data rate digital link, which equipment is provided with a circuit (6') for detecting and handling alarms, and a circuit (3) for recovering the bit rate from the digital stream. An OR gate (12) associated with dividers (10, 11) implemented in a high speed ECL technology generates a repetitive 1000 pattern on which a sequence is based, and switching device (13) also implemented in high speed ECL technology serves to insert sequences of said pattern into the digital stream to constitute a remote signalling message. The switching device is controlled by message-building logic circuits made from slower I.sup.2 L or Schottky technology.

Apparatus for remote signalling on a digital transmission link

The method consists in momentarily replacing the data transmitted by a digital data link with a digital message comprising two non-consecutive sequences, with the first sequence being a prefix sequence and the other sequence being a suffix sequence. The period of time separating the prefix and suffix sequences is variable and encodes remote signalling data. FIG. 2 shows a message transmitter circuit fitted in digital link equipment for operation at a very high data rate, and provided with a circuit (6') for detecting and handing alarms and with a circuit (3) for recovering the bit rate from the digital stream. A pattern generator (10) serves to generate a 1000 pattern and its 0111 complement from the recovered check rate. An oscillator (20) has a period which defines the time interval separating the prefix sequence and the suffix sequence. This oscillator controls a sequencer (25) which in turn controls a prefix sequence building circuit (30) and a suffix sequence building circuit (40) both of which act via logic gates on a circuit for selecting pattern types and on switching means (19) for inserting the selected sequence into the digital stream instead data.

Method and apparatus for remote signalling on a digital transmission link

The method consists in momentarily replacing the data in a transmitted digital data stream by a remote signalling message which is built up from consecutive sequences, each of which is obtained by repeating a specific binary pattern chosen from a plurality of possible binary patterns which are generated from the second and fourth sub-harmonics of a clock signal at the bit rate of the digital stream, and from logical combinations thereof. FIG. 2 is a circuit diagram of a transmitter circuit for transmitting a remote signalling message. Said transmitter circuit is located in equipments on a very high data rate digital link, which equipments include a circuit (6') for detecting and handling alarms, and a circuit (3) for recovering the bit rate from the digital stream. Divide-by-two circuits (10, 14) and a logic gate (16) serve to generate three kinds of pattern from the recovered clock rate, namely: 0101, 0011, 1000. A sequencer (21) builds up sequences of patterns within a remote signalling message by means of a multiplexer (20) whose inputs are encoded with the message to be transmitted, a pattern generator selector circuit (11, 15, 16), and switching means (18) for inserting the remote signalling message instead of the digital stream.

Method and apparatus for remote signalling by substituting a message for

A circuit permits the output voltage of an amplifier to be limited for certain ranges of its input voltage by causing the amplifier to saturate for said ranges of its input voltage by reducing the power supply. The invention is applicable, for example, to eliminating or levelling the components of a signal whose amplitude lies within a certain range, without affecting any other components.

Circuit for limiting the output voltage of an amplifier

The invention relates to transmission systems and in particular to level regulators controlled by a pilot tone and used in such systems to correct variations over a period of time in the attenuation of the transmission system. The subject of the invention is a level regulator governed by a pilot tone whose gain control circuit locks in a mean position where there is a very low or zero value detected for the pilot tone. This locking is achieved by modifying the supply voltage of the error amplifier of the loop providing automatic gain control for the regulator. The invention is of particular application to cable transmission systems with repeaters.

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Bruyeres le Chatel, France

Jean-Claude Lacroix