Patent GB-547268-A (GB)
Title: Improvements in and relating to electrically-controlled visual indicators
IPC: H04M3/64
Filed: 1941-05-09
Abstract: 547,268. Electric signalling system. STANDARD TELEPHONES & CABLES, Ltd. May 9, 1941, No. 6024. Convention date, May 15, 1940. [Class 40 (i)] [Also in Groups XXXIX and XL] A visual indicator such as a call indicator for telephone systems comprises a number of gas discharge tubes selected tubes being feebly and non-visibly ionized and the final display being made visible by the full ionization of the selected tubes. The call indicator, Fig. 1, comprises a number of areas, one for each digit, sub-divisions of which are selectively illuminated by gas discharge tubes. The left hand area indicates a 10000's digit of 1 or 0, the right hand area indicates one of four party line subscribers M, J, R, W, (4-digit lines only), and the remaining ones indicate in code the other digits of the number. The code comprises the sum of the unlit areas which are given the values 1, 2, 4, 5. The tubes of the 100's, 10's and units indicators, Fig. 8, comprise a cathode 2, Fig. 3, control anode 4, sustaining anode 5 and an anode 3 for fully and visibly ionizing the tube. The 10000's and party line tubes have no sustaining anodes. The tubes comprise cylindrical envelopes with flat top indicating portions. Methods of selective operation are described below. When ionized by the control anode the cathode glow is local and weak and, in the case of tubes with sustaining anodes, at the bottom of the cathode, but when fully ionized by anode 3 the top of the tube is filled with glow. The connection is extended to the operator's position by register-controller 10 in known manner and when trunk circuit is seized relay ST causes switch SW to associate the call indicator circuits with the trunk, relays TT and TTA being operated followed by CE, CEA and LP. The operation of CE energizes all the control anodes of the 10000's and 1000's banks and all the sustaining anodes of the 100's 10's and units' banks. Further, since CEA is slightly slow to operate, the control anodes of the lamps of the three last mentioned banks are momentarily energized by CE and as their cathode circuits are permanently completed, the lamps are weakly ionized. The digittransmitting code employed is the standard one consisting of four periods for each digit in the first or third of which a single weak positive impulse may occur, while weak or strong negative impulses occur in the second and fourth periods. Relays P and N respond to the positive and negative impulses respectively and marginal relay M to the strong negative impulses, relays W and Z, Fig. 5, being controlled by the negative impulses so that Z causes extension on the connecting chain, Fig. 6, at the end of each digit. Relay W. operates on commencement of the 1st negative impulse (2nd period), Z pulls up on its termination, W relapses at the commencement of the 2nd negative impulse (4th period) followed, by Z at the termination thereof. The positive and strong negative impulses are repeated by P and M to the lamp control circuits shown in Fig. 7 which are conditioned for the reception of successive digits by the chain, Fig. 6. The 10,000's and party line digit which may be 1-5 or 0 is received by relays AR to DR which select a lead M, J, R, W, I, O at the foot of Fig. 7 to complete the circuit to the cathode of one of the 10,000's and party line tubes to ionize it weakly. The 1,000's digit is received by relays AA-DD which are selectively energized to remove the ground connections, normally existing over leads T1-T4, of the cathodes of the 1,000's bank, to de-ionize selected tubes. The transmission codes of the 1,000's digits differ from the codes of same 100's. 10's and units digits and relays AA-DD are used for purposes of translation. The control of the tubes for the other digits is effected directly by relays M and P and consists in selectively shunting the energized sustaining anodes of the corresponding banks. After digit transmission, with the chain, Fig. 6, fully operated, the register-controller may send a strong positive impulse or not depending on the type of sender, and the chain relay VA changes the receiving loop so that N may respond to the positive impulse. This relay or in the absence of the impulse the relapse of a previously operated relay K operates FD and ED whereupon the main anodes of all the lamps are energized and those which are still ionized are brought to full brilliance. Relay KA operated over wiper SWC extends the connection to the operator who eventually releases the indicator by operating key 69 which releases all operated relays, except 68 which holds KA.