Patent GB-711506-A (GB)
Title: Improvements in or relating to telecommunication or like systems
Inventor: KEATING JOHN HENRY
IPC: H04M15/08
Filed: 1951-10-19
Abstract: 711,506. Exchange systems. AUTOMATIC TELEPHONE & ELECTRIC CO., Ltd. Sept. 29, 1952, [Oct. 19, 1951], No. 24406/51. Class 40 (4) [Also in Group XXXVT] In a circuit arrangement for receiving digits forming a number, means for controlling the display of the number are provided in common to a plurality of incoming circuits ; a first choice control means is taken into use if it is available, and a chain circuit is completed to take into use a later choice control means if the first choice control means is unavailable. The drawings show equipment for the reception and display at an operator's position of the digits forming the number of a calling line. Incoming call.-The operator inserts the cord circuit plug AP in the appropriate jack and operates the usual speak key KS to associate the cord circuit CC with an idle position circuit PC. The required connection is set up in the usual manner. Identification of calling line.-The operator momentarily depresses a key KLA to bring up a relay DR.. This applies an earth pulse to a start lead IFS, connects the cord circuit to contact banks PF1 and PF2 in a position finder and storage relay set PFSRS, and applies a resistance-battery marking to bank PF8. The release of key KLA brings up relay RS. If PFSRS is idle, relays IR and CO therein are in the operated condition as shown. The operation of CO breaks a chain circuit and enables astart lead such as 1FS to be extended to the idle PFSRS. If a fault should prevent the key KLA obtaining an idle position finder and storage relay set, a second key KLB provides access to the chain at a different point. Assuming that the first choice PFSRS is available, the earth pulse on the start lead 1FS brings up high-speed relay STA which releases CO to extend the start lead 1FS to the second choice position finder and storage relay set 2SRS. Relay STB operates and brings about the energization of alarm relay RA and latch magnet LM in series. Magnets DM are now energized alternately to drive the wipers PF1-8 of a motor uniselector in search of the marked position circuit PC. When wiper PF8 encounters the resistance-battery marking, high-speed relay TA is operated to bring up high-resistance relay H and de-energize LM and RA, stopping the switch PF. Relay HA operates and connects the display circuit DC, Fig. 4, to a display control circuit CDC, Fig. 8. The operation of relay H also connects the cord circuit CC to a voice-frequency receiver VFR, applies positive battery to the lead TA in order to start the distant identification equipment, and extends earth over lead 20 to a control relay set CRS, Fig. 7, where a relay BH is operated. Reception of signals representing number of calling line.-Each digit of the number is represented by a code of four elements, each element consisting of a marking pulse of 750 c/s. alternating current or an equivalent period with no signal, the four elements being preceded and separated by spacing pulses of 600 c/s. A.C. Each digital pulse train contains either one or two marking pulses. In the voice-frequency receiver VFR a relay X responds to the marking pulses and a relay Y to the spacing pulses. The relays X and Y are represented in the drawings only by their contacts x and y, Fig. 7. At any given time, one of each of the pairs of relays A, B and C, D is energized, A and C being energized, together with BB and BA, before the reception of the initial spacing signal. Circuits PHI, PH2, preferably in the form of relaxation circuits having two stable conditions of equilibrium, are so arranged that the response of relay Y to each spacing pulse after the first transposes the conditions of relays A and B, while relays C and D are similarly transposed at every second spacing pulse. Relays A, B, C, D interact with relays 1CA and 1CB to complete marking circuits from contact x to relays 1W, ... , IZ, 2W, ..., 2Z in turn, so that the first digit is stored on relays 1W-1Z and the second on 2W-2Z. At the beginning of the second digital pulse train, relay 1HA operates and causes the first digit to be transferred from 1W-1Z over leads 22, 24, 26, 28 to relays 1SW- 1SZ in PFSRS. The second digit is later transferred to relays 2SW-2SZ by the operation of relay 1HB which also extends earth over lead 31 to bring up relay CA in PFSRS. The third digit is first stored on 1W-1Z and then transferred to 3SW-3SZ, the fourth digit is stored on 2W-2Z and then on 4SW-4SZ, and the fifth digit is stored on 1W-1Z and finally transferred to 5SW-5SZ. In PFSRS, relay CB is energized at the transference of the third digit and CC at the transference of the fourth digit. The operation of relay 1HA to transfer the fifth digit, following the 21st spacing pulse, also extends earth over lead 30 to operate relay HA in PFSRS, this earth being further extended over lead ST to the display control circuit CDC, Fig. 8. After the end of the 21st spacing pulse, which is the final signal from the distant identification equipment, relay Y in the voice-frequency receiver remains deenergized and allows slow-releasing relay BB to fall back. This places earth on lead 21 and brings up relay F in PFSRS. Relays H, DR, TA, STA, and STB are thereby released and the earth connection is removed from lead 20 so that relay BH falls back and initiates the release of the control relay set CRS. Display of number.-When earth is extended over lead ST to the display control circuis CDC, Fig. 8, as described above, a relay P it operated and extends battery over wiper DS2, strapping between terminals 80 and 81, and lead BC to PFSRS and thence over wiper PF4 to the display circuit DC where it brings up a brilliance control relay (not shown) to allow the beam of a cathode ray tube CRT to impinge on the screen. Selectors 1FSX, 1FSY, Fig. 5, each comprising a pyramid arrangement of contacts of relays 1SW-1SZ, select an appropriate pair of potentials from those supplied by figure generators FGX, FGY and feed them over wipers DS5, DS4 to the deflection plates of the tube CRT so that the beam traces the first stored digit on the screen. Relay P interacts with magnet DSM to step wipers DS1-5, and the stored digits are displayed successively in a line across the screen, an increasing shift potential being supplied over wiper DS3 and selected pairs of figure potentials from FGX, FGY over wipers DS5, DS4. The beam is suppressed while the switch DS is stepping between contacts, relay P being then released. When switch DS reaches its home position, the earth on lead ST is removed so that relay HA falls back to initiate restoration of the equipment to normal. The re-operation of relay CO opens the chain circuit to make the equipment once more accessible to an operator. If a display of only four digits instead of five is required, the strap between terminals 80 and 81 is removed and it is arranged that the distant identification equipment transmits no marking pulses for the first four code elements. The first digit of the number is then stored on relays 2SW-2SZ, and there is no battery connection to the brilliance control lead BC when wiper DS2 is on contact 1, so that no digit is displayed in the first position. If a mixed numbering scheme is in use, requiring a display of either four or five digits, the strap between terminals 80 and 81 is omitted while straps are added between terminals 82 and 83 and between 84 and 85. Three relays WC, XC, ZC are arranged to operate at the same time as storage relays 1SW, 1SX, 1SZ so that for a five-digit display as described above not more than two of relays WC, XC, ZC are operated at any time. For a four-digit display, a code signal including marking pulses as the first, second, and fourth elements is transmitted in place of the first of the five digits, so that all three relays WC, XC, ZC are energized to disconnect contact 1 of wiper DS2 from the brilliance control lead BC. Forced release of the equipment is effected if no signals are received by the voice-frequency receiver within a predetermined time or if fewer than the requisite 21 spacing pulses are received.