Patent GB-781854-A (GB)
Title: Improvements in or relating to electrical signalling systems
Inventor: DAVISON ALAN
IPC: H04Q1/30
Filed: 1954-02-03
Abstract: 781,854. Automatic exchange systems. AUTOMATIC TELEPHONE & ELECTRIC CO., Ltd. Jan. 27, 1955 [Feb. 3, 1954], No. 3150/54. Class 40 (4). In a system for transmitting numbers, in binary form, checking arrangements are provided in which a first binary counting circuit at the transmitter counts the total of ones in the numbers to be transmitted and transmits this total before the transmission of the numbers, the total being injected in complementary form into a second binary counting circuit having the same capacity as the first and to which the ones of the received numbers are subsequently added, whereby if the number of ones counted by both counting circuits is the same the second counting circuit registers its maximum count. Figs. 1-15 and the related description are also to be found in Specification 781,856. General description. Sender, Fig. 1. When a register at the sending end has stored its full complement of information it is connected to a free sender controlled by a sequence counter. The information in the register is stored on twoposition devices such as relays or gas tubes and a signal from the sender causes all such devices in one of the two positions to signal the storage circuits in the sender. The storage circuits together with prefix and binary check count circuits are arranged in a co-ordinate scanning field. The field consists of gas tubes, each level in turn being primed by level counter, while the tubes in a level are pulsed in turn by a contact counter which scans at the rate of 400 tubes per second. At the end of each cycle of the contact counter the level counter steps on. The result of the first scan is that the information displayed by the register is stored in the sender, and the binary check count circuit has counted the total of " ones " in the binary representation of the numerical information. If the receiver at the distant exchange is free the sender scans its storage circuits again, this time at 50 tubes per second, and all the information beginning with the prefix signal and including the binary check is transmitted in the form of " mark " and " space " impulses. If the message is received correctly the receiver returns an " O.K." signal to the sender which signals the register and restores. If this signal is not returned within a predetermined time, the sender waits until a " receiver free " signal is received and then repeats the message. If there is still no acknowledgment from the receiver the sender clears itself without signalling the register. Receiver, Fig. 2. A signal from the sender starts a multivibrator to cause a 50 i.p.s. counter to drive a contact counter and a level counter which scan a field comprising tubes from the prefix, binary check, supervisory, and storage circuits, the scanning being at the same rate but slightly out of step with the pulses received from the corresponding elements in the sender. The binary check count is tested against the component parts of the message and if satisfactory an " O.K." signal is returned to the sender and the received information is transferred to a register. The receiver then restores. If a fault is detected the receiver restores without returning this signal. An " early transfer " facility is provided to enable certain routing and supervisory signals to be transferred to a register before the complete message has been received. Detailed description. A prefix indicates the figure in which a tube occurs. Each lead is shown with the number of the figure to which the lead connects. The system includes a number of step-by-step counting circuits such as Fig. 13 in which a self-extinguishing tube, say 13VR2 fires the related counter tube 13VC2 which then extinguishes the preceding counting tube 13VC1 in the manner claimed in Specification 781,855. Initially tubes 4VD2, 5VC9A, 8VC11A, 15VC3 are fired. If the junction line to which the sender is connected is free potential on the return leg MCB, Fig. 16, biases tube 16VT2 of the receiver supervisory circuit beyond cut-off so that 16VT1 conducts and relay REC energizes. Lead PL is thus connected to a supply of 400 pulses per second. The first pulse strikes 5VR1 which self-extinguishes and strikes 5VC1 to set the sequence control circuit to'first position. 5VR1 also fires 13VR5 of the sequence work circuit. Seizure of sender. When a register requires a sender it operates relay TS, Fig. 3, in a sender. If the sender is free the removal of an earth shunt by contacts ts1 fires 3VW1 in the supervisory circuit to the next pulse on lead PS1. Relay ON pulls up and returns a " sender free " signal over lead PS. The register then earths lead SS to energize relays A and HTS. HTS supplies H.T. to leads HT2, HT3, but relay A energizes B to cut the bias supply over lead RB to tubes 9VBA1-9VBAn after they have fired, so zeroizing the binary check circuit. Tube 4DV1 fires after a short delay to advance the sequence control circuit to its second position with 5VC2 fired. Momentary firing of 5VR2 also strikes auxiliary tube 7VC2A in the level counter and, through 13VR1, sets the sequence work circuit to first position by striking 13VC1 to operate relay MB. Transfer from register to sender. MB marks lead B, Fig. 13, to cause the register to bias those leads DG, DH connected to the trigger electrodes of store tubes 11VP1, 12VP1 and count tube 12VP3 in every numerical storage circuit corresponding to an operated storage device in the register. The storage circuits are now ready for the high-speed scan. The sequence control circuit moves to third position with 5VC3 fired. The momentary striking of 5VR3 also fires 6VE2 in the 400/50 i.p.s. counter so that 6VR1A pulses lead AD at the rate of 400 i.p.s. as long as 6VE2 is fired. These pulses control pulse-inverting tube 4VT2, a chain of pulsed - H.T. supply tubes 4VT3- 4VT7, and contact counter driving tube 4VT8 which pulse leads PHTA-PHTE and AK, AZ. These leads control the contact counter, Fig. 8, to pulse leads 1x-10x and 0sx-9sx at the rate of 400 i.p.s. The tenth " x " pulse, generated by cathode follower 8VT1, pulses all the self-extinguishing repeater tubes 7VR1-7VR15 of the level counter which is stepped on after each cycle of the contact counter. By this means the leads 1y-15y are biased in turn, beginning on this occasion with lead 2y. since 7VC2A, as previously described, is already fired. The mark tubes 11F1-11VFn, (not shown), 12VF1- 12VFn (not shown) of the miscellaneous and numerical storage circuits and 9VF1-9VFn of the binary check count circuit have their trigger electrodes connected to a co-ordinate scanning field the axes of which comprise the 10 " x " pulse and 15 " y " bias leads. The mark tubes 9VF1-9VFn associated with the binary check count are connected to lead 1y and are therefore not pulsed in the high-speed scan. In the miscellaneous storage circuits the firing of each mark tube such as 11VF1 strikes the associated store tube such as 11VP1, if primed from the register as already described. In the numerical storage circuits both the store and count tubes 12VP1, 12VP3 primed from the register are similarly struck. The count tubes extinguish at the end of the anode pulse on lead PHTC after pulsing the inlet to the first stage of the binary check court circuit over leads AA, AB in series. Operation of binary check count circuit. The binary check count circuit, as already described, starts with the tubes 9VBA1-9VBAn fired. The first pulse on lead AB changes over the pair 9VBA1, 9VBB1 and the second pulse changes them back again, also firing 9VN1 to pulse the second pair, and so on. At the end of the high-speed scan the circuit registers the number of " ones " in the binary representation of numbers transferred from the register to the numerical stores such as Fig. 12. At the end of the scan level 15 pulse repeater tube 7VR15 fires to strike 13VR2 in the sequence work circuit so that 13VC2 fires and relay CF pulls up. 13VC1 extinguishes and relay MB restores. CF extends earth over lead SR to the register to indicate that the sender has received all the stored information. Level 1 pulse repeater tube 7VR1 then fires to strike 7VC1, 6VE1 in the 400/50 i.p.s. counter, and 5VR4 in the sequence control circuit. 6VE1 extinguishes 6VE2 to stop the train of pulses on lead AD. The contact counter stops with 8VC11 fired. 5VR4 fires 5VC4 and pulses lead DJ to fire 13VR3, 13VC3 in the sequence work circuit, so operating relay HTK. 13VC2 and relay CV restore. HTK applies H.T. to the anode of 3VW2 of the supervisory circuit. Signalling distant exchange. The sender now tests whether the distant receiver is free. If a free signal is returned REC, Fig. 16, remains operated but if a busy condition exists on lead MCB tube 16VT2 conducts and 16VT1 cuts off so that REC falls back. When the junction becomes free REC re-operates after a slight delay designed to guard against spurious impulses. Sending. When the junction is free the next pulse on lead PL fires 5VR5 to strike 5VC5, the send initiating counter tube 6VC7A, and tube 6VE3. The level counter is now in first position with 7VCI fired and the binary check count circuits associated with bias lead 1y are ready for scanning. The next pulse fires 6VP8 to strike 6VC8 so that the 400/50 i.p.s. counter is now ready to supply pulses from the cathode of 6VR1 at the rate of 50 i.p.s. These impulses are delivered over lead AD to pulse inverting tube 4VT2 and the pulsed- H.T. and contact counter driving tubes so that the contact counter circuit, Fig. 8, scans at 50 i.p.s. In the case of the pre-fix elements used to distinguish at the receiver between an actual and a spurious signal, firing of a tube 10VF pulses the common lead SC. In the case of the binary check a send tube , say 9VP1, fires if primed by 9VBB1 of the binary pair. The firing of a mark tube 11VF1 or 12VF1 in the miscellaneous and numerical storage circuits' fires the corresponding send tube 11VP2 or 12VP2 if primed fr