Patent GB-1233075-A (GB)
IPC: H04J3/06
Filed: 1968-05-31
Abstract: 1,233,075. Multiplex pulse code signalling. COAL INDUSTRY (PATENTS) Ltd. 30 May, 1969 [31 May, 1968], No. 26240/68. Heading H4L. In a data transmission system particularly for transmitting digital data in time division multiplex to and from a mining machine, the transmitter station and the receiver station each include a stepping switch, a group of stages of each switch being interconnected by gating means to identify synchronism between a transmitted and received signal and to produce an inhibiting signal in the receiver station in the event of loss of synchronism, the gating means in the receiver station including a gate to control the operation of a pulse generator feeding the receiver stepping switch. Transmitter, Fig. 1.-A clock pulse generator 10 supplies pulses to a fast stepping switch 12 having twenty-four stages, the first four stages being interconnected by gating circuits, Fig. 3 (not shown), in a transmitter drive circuit 16 so that a synchronizing signal of alternate positive and negative pulses is transmitted to line via a transformer winding 32. When synchronization has been completed the fast stepping switches 12 and also slow stepping switches 28 at the transmitter and receiver are synchronized, even numbered and odd numbered stages of the switches 28 being used for transmission to and from the machine respectively, the second stages being the first to be energized to start transmission to the machine. The even stages 6 and 8 cater for analogue signals which are sampled at 24, coded at 18 and stored at 22, transmission taking place during the energization of stages 6 to 12 of fast stepping switch 12 and being repeated during the energization of stages 13 to 19. Digital signals are allotted to stages 10, 12, 14 of selector 28 and are sampled at 26 and supplied via a digital-to-digital coder 20 to the store 22 for subsequent read-out. The slow stepping switch 28 is stepped on each time stage twenty-four of the fast stepping switch is energized. Receiver, Fig. 2.-Incoming signals are supplied via winding 36 of the input transformer to intial and final stores 44, 46 and a synchronizing receiver 40. The receiver also includes stepping switches 12 and 28 corresponding to those at the transmitter, a digital-to-analogue converter 48 and digital decoder 49 corresponding to the coders at the transmitter. The synchronizing receiver 40 is controlled by the incoming sync. signal and the first four stages of the fast stepping switch 12, which are interconnected by logic circuitry 42, Fig. 4 (not shown), in turn controlling the slave pulse generator 10 operating the stepping switch 12. The first sync. pulse starts the slave pulse generator 10, stage 2 of switch 12 being energized. The second sync. pulse which is negative sets a bi-stable (128), the third sync. pulse sets a bi-stable (132) and the fourth sync. pulse set a bi-stable (136). The output of the bi-stables are combined by logic circuitry such that if the system is synchronized the second stage of slow stepping switch 28 is energized and switches 12, 12, 28 continue to step. If synchronization is faulty the pulse generator 10 at the receiver is stopped and stops the switch 12, the bistables are reset and the receiver is ready to respond to the next set of sync. pulses.