Patent GB-1372924-A (GB)
Title: Time slot distributor for a multiplex system for telegraph or data transmission
IPC: H04J3/24
Filed: 1972-01-11
Abstract: 1372924 Multiplex pulse code signalling SOC ITALIANA TELECOMUNICAZIONI SIEMENS SpA 11 Jan 1972 [11 Jan 1971] 1179/72 Heading H4L A transmission distribution unit for combining digital signals on a plurality of lines in a time division multiple access system and assigning time slots to the respective lines in accordance with their transmission speed, comprises a generator for generating pulses of variable length whose possible durations are equal to all multiples of time slots which may be assigned to the respective lines, a plurality of memories each associated with an individual line and arranged to memorize the number of time slots allotted to that line, a scanning network receiving information from the memories to generate sequential scanning signals of a duration fixed by the pulses from said generator only for those lines which are assigned time slots, each scanning signal causing the information stored in the associated memory to reach the generator as a control signal and at the same time to assign the time slots to the corresponding line, and an assignment message generator for indicating for each line the number of time slots allotted to it and the order of assignment. At the receiver the assignment messages are extracted and similar apparatus controls the distribution of the signals to the appropriate lines. As described, Fig. 3 (not shown), each frame F comprises a plurality of subframes K and each subframe consists of a preamble for synchronizing the receiver, a plurality of time slots each of one or more bits which are divided between the respective lines as previously described and one assignment bit which forms part of the assignment message. The assignment message extends over a plurality of frames designated a multiframe and consists of a synchronizing word followed by assignment words each relating to one line and stating the number of time slots assigned to that line. Transmitter.-Each station comprises a multiplexing and transmitting unit MT for the digital signals received on lines L 1  to L n  which are transmitted in a subframe K. The distributer includes memories Me 1  to Me n , one for each line, which are set manually to store the number of time slots assigned to that line. A scanning network Sc receives outputs N 1  to N n  from the memories indicating which lines are to be assigned time slots and generates successive signals G 1  to G n  only for those lines, each signal lasting for a period determined by the duration of a pulse A from a generator Ga. Signals G 1  &c. enable corresponding gates A 1  &c. so that the information stored in the memories is passed in succession to the generator Ga which produces pulses A of duration representing this information. Signals G 1  to G n  are also supplied to the apparatus MT to control the transmission of the signals from the lines L 1  to L n  respectively. Generator FM is controlled by the memories to form the assignment message which is also supplied to apparatus MT. Receiver.-All the signals of a frame F are received in the receiving and demultiplexing unit MR and supplied to a device EM which extracts the assignment message and transfers into memories Me 1  to Me n  the information P regarding the number of time slots for each line (Signals I 1  to I n ). The memories inform the scanner Sc by signals N 1  to N n  of the lines which are to be scanned in each frame, the duration of the scanning signals G 1  &c. being controlled by the duration of pulse A from the generator Ga. Signals G 1  to G n  enable corresponding gates A 1  to A n  so that information from the memories is presented to the generator Ga to control the duration of pulse A. Signals G 1  to G n  control apparatus MR to distribute the received data to the appropriate lines. Local receiving lines are interconnected with any distant transmission line of the system by means not described.