Patent GB-684079-A (GB)
Title: Improvements in or relating to magnetic recorders, particularly for storing signals in telephone systems
IPC: H04M15/10
Filed: 1951-08-24
Abstract: 684,079. Automatic exchange systems. WESTERN ELECTRIC CO., Inc. Aug. 24, 1951 [Sept. 7, 1950], No. 19989/51. Class 40 (iv). [Also in Group XL (b)] A magnetic recorder comprises a continuously moving surface of magnetic material, a plurality of pick-up devices and a plurality of recording devices located adjacent said surface and means responsive to a predetermined pattern of signals received from a plurality of pick-up devices for recording signals by one of said recording devices. The invention is applied to a call annunciator which may also register the called number. Call annunciator, Fig. 1. A drum 104, with a magnetic surface divided into delay and storage parts, is continuously rotated at high speed and co-operates with a number of recording and pick-up heads. Two pick-ups 50, 51 generate +ve timing pulses and a - ve synchronizing pulse, respectively, each revolution. The timing pulses are amplified at 60 and pass through a delay line, Fig. 2 (not shown), to control the stepping of the beam of a cathode-ray tube 25 over a number of targets such as 32, the synchronizing pulse restoring the beam to the first target at the end of each revolution of the drum. An idle line, say 14, maintains its target 32 at ground potential so that no record is made in the related spaces on the drum, but initiation of a call by closing contacts 10 makes the related target 32 more negative so that when the beam falls on the target, the secondary electrode 37 becomes more positive and applies a +ve pulse to diode 208 in gate 201. The absence of a signal in the related storage part of the drum causes pick-up 115 to apply a +ve pulse over its O output lead to rectifier 206 and a synchronizing pulse applied to 204 thus causes the gate 201 to apply a +ve pulse over the X lead and amplifier 110 for the recording head 111 to register X in the related cell of the delay part of the drum, When this cell reaches pick-up 112, it generates a voltage which is amplified and fed to recording head 114, the X originally recorded being cancelled when it reaches erasing head 118. The X recorded by 114 reaches pick-up 115 at the same time as the cathode-ray beam again falls on the target 32. The head 115 applies only a low voltage this time to the O output lead, and gate 201 is thus unable to open so that further X signals cannot be recorded by head 111 at this time. The pulse from electrode 37 was also applied to rectifier 216 in gate 211 to cause head 121 to record an X which is transferred via 122, 124 to the storage part of the drum, the original record being erased at 128. The X recorded at 124 is read at 125 and erased at 129. However, as long as the loop is closed, the X is repeatedly recorded at 121 and read at 125. When dial contacts 20 open, the recording of X at 121 ceases and pick-up 125 energizes the O output lead, while the X originally recorded energizes the X output lead of pick-up 115, these potentials combining in gate 251 to raise the potential of lead XO and energize a timing circuit 270. At the same time, pick-up 135 energizes its O output lead, which combines with the outputs of pick-ups 115, 125 to raise the potential of lead XOO to cause an X to be recorded by head 131, this X being subsequently transferred to recording head 134 and being read later by pick-up 135, so that no further pulses occur on lead XOO at this time. The X recorded at 131 is erased at 138. If the contacts 20 reclose, head 121 records an X which is transferred to the storage section and read out by pick-up 125. As pick-ups 115, 125, 135 all read X at this time, the XXX lead from gate 251 is energized to signal rectifiers 223, 232 so that heads 131, 141 record O and X respectively, these signals being transferred to the storage section so that the signals read by heads 115, 125, 135, 145 are now X, X, O, X. The last of these signals is used as a calling signal, the X output lead from amplifier 146 being connected to register and display apparatus. Indicating calling line. A binary counter comprising a number of double triodes 1011, 1012, &c. is zeroized by a delayed synchronizing pulse from pick-up 51 and is stepped with the beam of the cathode-ray tube by the delayed timing pulses from pick-up 50. If the indicating apparatus is not already in use, when a calling condition energizes the X output lead of amplifier 146, all the rectifiers 163-156 are subjected to high potential and cathode follower 911 pulses the diodes of gate circuits 731, 732, &c. so that the setting of the binary counter is transmitted to corresponding gasfilled tubes 1040, 1041, &c. and so to indicating tubes 1070, 1071, &c., whereby the identity of the calling line is indicated to the operator. To restore the indicating circuit, key 1051 is thrown to reverse trigger pair 1050, gates 731, 732, &c., timing pulses firing tubes 1060, 1061, &c. to restore tubes 1040, 1041, &c. and 1070, 1071, &c. Condenser 1053 charges until trigger pair 1050 responds to the next timing pulse, when the apparatus is ready to respond to the next calling condition. Release of call. When contacts 10 in line 14 reopen, after a predetermined number of signals on lead XO, timer circuit 270 operates to apply O signals to channels G1 and J. Registration of called number. Absorption of accidental impulses, Figs. 4-7 show an embodiment which registers dialled digits, the figures being arranged as shown in Fig. 19. In the manner already described signals from the cathode-ray scanner 44, Fig. 6, are applied to gate circuits 201, 211 to control recordings in channels G1, G2. The outputs from channels G1, G2, H, J control a combining circuit to apply high +ve voltage to appropriate output leads. Closure of the loop causes X to be recorded in channel G1 and repeatedly in channel G2 to energize lead XX. When contacts 10 or 20 in the loop open, leads XO and XOO are energized, the latter causing X to be recorded in channel H. In the succeeding revolutions of the drums, if the contacts should remain open, lead XO feeds the left-hand terminals of gates 431, 421 ... 401, these terminals (other than 431) being also fed by the output of the preceding B channel, to record X successively in channels B1, B2 ... B7 and eventually in A, to indicate that the subscriber has hung up, output of channel A then restoring the circuits to original condition. An accidental or single first impulse is thus absorbed without affecting the register. If the loop closes again for an appreciable time it energizes lead XX to record O in any B channels which had previously recorded X. Lead XXX is then energized to apply potential to terminals 5 and 7 of all gate circuits associated with channels K1-K88, which are also subjected on terminals 4 and 6 to the potentials from the pick-up of the preceding channel. In this case, therefore, O signals are transmitted to all the K channels. Lead XXX also registers X in channel J and O in channel H. During the next few revolutions, lead XXOX is energized to record X in channels F1, F2, and so on until X is recorded in channel E, which energizes lead XRE at the next revolution to cause the recording of O in all the F channels and in channel J. In the succeeding revolutions, X appears only in channels G1, G2 as long as line 14 remains closed. Thus,_one or more openings of line 14 followed by closings long enough to give a full count in the F and E channels do not affect the register and such impulses are discarded. Registration of dialled digit. The drum revolves more than once during each opening and each closing of the dial contacts. Assume now that digit 2 is dialled. At the first opening of the contacts, lead XOO energizes to record X in channel H and lead XO energizes to record X in channel B1 followed by B2 and so on for the duration of the opening. The line recloses to record X in G2 and cancel the registration in the B channels. Lead XXX now registers O in channel H and X in J so that lead XXOX becomes energized to record X in channel F1. The second opening of the dial contacts registers O in channel G2 so that lead XOO records X in channel H while lead XO deletes the record in the F channels and registers X in B1 and subsequent channels until reclosing of the dial contacts energizes leads XX and XXX. XX cancels the registration in the B channels, XXX records O in H and X in J and applies voltage to both sides of all gates.relating to K channels, the first of which receives an X output from channel J to record X in K1. The output of channels G1-J is now XXOX which causes the recording of X in successive channels F1, F2 and so on and since the dialled digit is complete, X is eventually recorded in channel E, which restores channels F and E at the next revolution and energizes lead XRE to record O in channel J. Lead XRE together with leads from channels K1, K2, the first in the example carrying an X, causes combining circuit 612 to energize lead 613 which energizes the gate circuits of all the K channels so that X is now registered in K1 and K2. Moreover, lead 613 causes X to be recorded in channel D1 to show that the first digit has been recorded. When the loop reopens for the start of the next digit, the process proceeds as described above but at the energization of the K gates, the O previously recorded in J is entered into K1. In this manner successive digits are entered in the K channels interspaced by single O's, and the number of channels D1-D7 bearing X's indicates the number of digits registered. At the end of dialling, X is recorded in the F and E channels to shift the registration one step along the K channels, the energization of lead 613 then entering X in channel C to show that all the digits have been registered. The called and calling numbers are indicated by apparatus similar to that already described with reference to Fig. 1.