Patent GB-333259-A (GB)
Title: Improvements in or relating to automatic and semi-automatic telephone exchange systems
IPC: H04Q3/42
Filed: 1929-05-14
Abstract: 333,259. Standard Telephones & Cables, Ltd., (Deakin, G., and Polinkowsky, L.). May 14, 1929. Automatic exchange systems. - In a system, in which the conversation switches are controlled by common control switches individual to a switching stage, the same final selectors are. used for extending both toll and ordinary calls. Ringing is applied automatically on ordinary calls but by the operator in toll connections. Special switches are provided for intercepting existing cells, but these, are controlled bv the control circuits available for ordinary traffic. The invention is described applied to a system in which marker switches send back revertive impulses to a register controller, the conversation switches (power driven) then hunting for marked terminals. General operation Fig. 15. A calling line S is connected by two line finders LF1, LF2 to a register controller RC which stores the number dialled. A selector IGF and control switch ICF are seized, and as the control switch moves over the outlet groups it sends back impulses. When the controller is counted out, the control switch puts marking potential on the wanted group of outlets and the selector IGF hunts for a free circuit in the group marked. The next two digits operate 2GF and FF in a similar way, leaving FF ready to step onto the first line in the tens group required. The control switch FCF then sends back impulses for the last digit and switches FCF and FF step together onto the line required. When the controller is counted out the line is tested by FF which connects ringing if the line is free and returns busy tone if it is engaged. Hunting over P.B.X. groups is arranged for. If the call originates from a toll operator TB the switch train TGF, 2GF, FF responds to the call, but an initial setting of the register controller prevents the automatic connection of ringing to a free line. For breaking in on engaged calls the train TWGF1, TWGF2 and TWFF is used. the register controller and control circuits being those used for ordinary connections. - Connections to and from junctions and to operators are also described. The switches are all uni-directional non-homing power driven switches arranged with wipers at 180‹ which wipe in turn over different contact banks. Local connection. Non-numerical switches. Figs. 1, 2, 9. When a call is made Lr (Fig. 1) pulls up energizing Fsr and common start relays Asr of the first line finders which search for the calling line. If there are no free finders lamp LGL lights. When the calling line is found Ltr energizes, broking the circuit of PF and energizing Csr. The second line finders are divided into four sub-groups, and if less than a predetermined number of finders in the first sub. group are free and commence hunting, finders in the second group are started, and if these are busy the third group starts, and so on, lamp SGL lighting if there are no free finders. When Csr pulls up, Hsr and Bsr of the first group energize, Abr pulling up if there are no free finders to connect the second sub-group. Magnet PL (Fig. 2) energizes in series with Sgr (Fig. 1), and when the calling circuit is reached Ar energizes the circuit extending over a contact of lEclr of a free control circuit (Fig. 6). Relay Ar breaks the circuit of PL and energizes Cr. Br and Dr pull up, Dr connecting earth to the c wire energizing Cor (Fig. 1) which releases Lr and Ltr to prevent further hunting. Sr energizes over the calling loop. Relay Arr (Fig. 9) pulls up and starts the register finder hunting for the calling line. When the marked terminal d (Fig. 9) is reached Crr pulls up breaking the circuit of PR to stop hunting. Err energizes and connects dialling tone from D over TC to the calling line. Registration of number, Fig. 9. Sr (Fig. 2) responds to the digits dialled which are repeated by Hr in turn to the registers SW. When the first register moves off normal Er (Fig. 2) and Ur (Fig. 9) pull up. Relay Er removes dialling tone and releases Cr, allowing Crr to fall back. Ir falls back at the end of the first impulse train allowing Jr to energize, followed by Kr which latter relay connects earth via relay Pr to bushes band battery to brush a. First selector, Fig. 3, and its common control circuit, Fig. 6. Relay Acr (Fig. 6) energizes from this battery connection which is also placed on the terminals wiped by brush i corresponding to the group selector in use. Ecr energizes magnet PC and brushes f-j move until the selector, Fig. 3, is reached, when Bcr pulls up breaking the circuit of PC and allowing Fcr and J 1 to energize. J1r connects the incoming impulsing leads to the control circuit. Pr (Fig. 9) and Dcr (Fig. 6) now energize in series and relays Rr and Nr pull up connecting Pr in a metallic loop across brushes a and b. Bcr relapses and PC re-energizes to earth at off-normal contacts N. The last 40 contacts wiped bv brush g (Fig. 6) are divided into 10 groups each of 4 terminals of which the second and third are earthed so that as the switch advances the brush g passes over the earthed groups sending back a pulse at each group to de-energize Pr (Fig. 9) enabling Qr to energize which steps SW1 one step. When SW1 reaches its 10th position the locking circuit of Rr is opened, and when Pr next de-energizes Rr relapses opening the fundamental circuit and allowing Srr to pull up. Mr and Qr energize stepping SW1 to its normal position. In the control circuit (Fig. 6) Dcr falls away when the fundamental circuit is opened. Gcr pulls up and magnet PJ (Fig. 3) energizes. The terminals f1-f10 on which the brush f is resting is connected to all the terminals d of the corresponding group and when a free line connected to a free control circuit (not shown) is reached Hcr pulls up, energizing Scr. Hunting stops, relay J2r energizes to switch through the circuit, the control circuit is released and is stepped back to normal over off-normal contact N. When the second digit has been completely stored in the recorder Kr again energizes and the second selector (not shown) is set in the same manner as the first selector, extending the call to a free final selector. Final selector, Fig. 5, and its common control circuit, Fig. 8. Ringing. The final selector control switch has 8 banks and 6 wiper sets, two of the sets (g, j) being double-ended and two sets (P, f) having wipers at 180‹ wiping over two con. tact banks. Wipers h, i are used to select the calling final switch, wiper i for centring the brushes, g is used for sending revertive impulses, f for marking the wanted line, and P for P.B.X. hunting. The earthed g terminals above the group used by h and i are earthed only after the selector to be used has been connected. The off-normal contact N remains made whilst the switch moves through 360‹. When the selector is seized 3Acr pulls up and 3Pc moves the wipers until the calling final switch is found when 3Bcr pulls up followed by F1r, 3Dcr (Fig. 8) and Pr (Fig. 9). Relay 3Dcr recloses the magnet circuit and the brushes rotate, impulses being sent back as g passes over earthed groups which are repeated by Pr to SW3. When SW3 is counted out the fundamental circuit is opened as before breaking the circuit of 3Dcr and 3PC and energizing 3Gcr. Icr pulls up and PF (Fig. 5) is energized moving the final selector in search of the marked line over which 3Hcr energizes. The final switch is then on the last line of the preceding group. When the fundamental circuit recloses 3Dcr energizes, followed by Ycr, and if 3Hcr has energized by this time Lcr pulls up. Lcr and Der interact moving 3PC and PF and sending back revertive impulses to count out SW4. The fundamental circuit is broken when SW4 is satisfied, 3Dcr de-energizes and Mcr pulls up energizing Xcr and releasing Icr and Ycr. F3r pulls up, F2r tests the called line, and F1r releases. The control circuit is released when F1r falls away, the switches being returned to normal by 3PC. If the called line is free F2r pulls up and ringing is connected over F4r, ringing tone being returned over MFR. When the called subscriber replies F4r pulls up releasing F3r. Completion of connection, release. Metering. The called p a, r t y is then connected through to Fig. 2 and S1r operates over the called loop. Fr pulls up, making Dr dependent on Sr. Speaking current is supplied from Sr and Sir. When the called party releases S1r falls away, and when the calling party hangs up Sr de-energizes followed bv Br and Dr. Fr falls away when Br has de-energized and during the period between the release of Dr and Fr metering current is con-, nected from Fr2 to operate SM in the calling line. Relay Br removes ground from the c wire and the switch train releases. Line busy. If the called line had been busy F2r does not operate, and when F3r pulls up busy tone from BT is con. nected to the calling line. Hunting over P.B.X. group. Back contacts of the cut off relays of PBX groups are connected to levels P in the control switch. When the switch is stepped on to an engaged first line of a group earth over wiper P energizes Pcr which disconnects Xcr and operates 3PC to advance the switch onto the next contact. Relay 3Hcr falls away and PF also advances one step. This sequence is continued until a free line on the last line of the group is reached. Calls to operator. Numbers 01, 02 are reversed for operator calls. If the first digit recorded-by the controller is 10, Tr (Fig. 9) pulls up preventing the registration of more than two digits. At the end of the selection of the second digit Dr (Fig. 2) operates releasing the controller. The call is extended over an ordinary first group selector (Fig. 3) to a special second group selector, which is similar to the circuit shown in Fig. 3, having 5 wipers, whence it is routed to operators equipment (Fig. 11). Relay 1Ar pulls up lighting the call lamp. The operator plugs in, operating relays 1Br (Fig. 11) and relays Er and Gr )Fig. 2). The calling lamp is