Patent GB-777345-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/42
Filed: 1954-05-19
Abstract: 777,345. Automatic exchange equipment. AGERWALA, P. M., KANT, R., and JOSHI, D. F. D. May 19, 1954, No. 14651/54. Class 40 (4). In a register-translator for use in Strowger step-by-step systems switching arrangements are provided whereby the register-translator may complete the transmitting function in response to the reception of subscribers' numbers comprising different numbers of digits, the switching arrangement being operated in response to a particular value or values of one or more respectively of the digits first dialled, and in operating, serving to provide circuit conditions for enabling the sender switch to operate to initiate the transmission of the units digit as soon as it is fully stored and for enabling the sender control switch to be stepped after the transmission of the units digit to the last position corresponding to the maximum number of digits, from which position it is released. The register translator shown is taken into use by the application of earth in the "A" digit switch to the " P " wire, and as a result relay chain A, B, BA is operated. Relay A is maintained by earth on PU wire from 1st code selector switch, and relay BA prepares a pulsing-out circuit and holds the A digit switch over the P wire. Relay A is impulsed (releasing and reoperating) by the dialled impulses received over lead PU and operates the vertical magnet VM of the BC switch through a winding of a relay C which relay, on operating, short-circuits its right-hand winding to become slow to release. The uniselector U which is stepped to position 2 through magnet UM by the release of relay C at the end of the train serves both as a digit distributer and a store for the 7th digit if such is required. The remaining incoming impulse trains operate the rotary magnets RM of switch BC, MM, CM, DM and UM in the case of a seven digit number. The BC switch is a six-bank switch the banks of which are wired to the translation field TF and to terminals CO, DCO and D(6) in a manner depending on the number of coding digits employed. The terminals 1-0 of the field are also multipled to contacts 2-11 of switch banks M2, C3, D3 and contacts 7-16 of bank U5. The wipers of the storing bank are connected in turn by a stepping wiper CN2, and a marking earth dependent on the wiper setting is successively applied to contacts of bank S4 to control the transmission of successive digits. Transmission is initiated by the stepping of switch U to position 3 whereby a self-locking relay SO is energized to prepare a circuit to the sender switch magnet SM and extend earth to the sender control switch magnet CNM. The sender switch is stepped by the 66 per cent make impulse springs IS1 and the first impulse of the first routing digit is sent when wiper S2 is stepped to contact 3. The impulsing continues until wiper S4 encounters earth over wiper CN2 to operate a relay SZ which releases relay CNM to step the control switch CN and release relay SO. Relay SO in releasing drives switch S to position 15 over interrupter contacts Sam whereat relay SO is again operated to step the switch to position 19. SO is then released and the switch returns to position 1 under the control of the interrupter contacts as above; the controlled stepping from contacts 15-19 providing an inter-digital pause of 400 milliseconds. Relay SZ is then released to reoperate relay SO over contact CN3 for the succeeding digit, and subsequent digits are similarly transmitted. Overrunning of the sender is prevented by C2, D2, and CN3 and U3, which open the circuit of relay SO until the succeeding digit is received. When wiper CN2 reaches contact 11 relay CO operates to release the "A" digit switch and clear down all the equipment. Relay CO is itself released when the switch BC is homed. If four routing digits only are required then the appropriate contacts of banks 5 and 6 of the BC switch are strapped to terminal DCO to step control switch CN2 quickly to position 7 for the transmission of the thousands digit. For setting up a connection to a line having a 6 digit number the BC switch is stepped by the second code and thousands digits but only a maximum of four routing digits may be provided since wiper 5 is called upon to regenerate the thousands digit, and wiper 6 effects circuit changes to discriminate the six digit numbers by operating relay D over a strapping to terminal D(6), to step switch CN to position 7 for the transmission of the thousands digit. Relay D also causes switch CN to step on to position 11 after the shorter number of digits have been transmitted. Calls involving three code digits only are dealt with by jumpering the appropriate contact in the bank below the last required routing digit to terminal CO. The banks of switches CN, M, C, D are divided into two and the switches have two duplicated normal positions. The embodiment may also be adapted for six digit calls having three code digits and for five digit calls. An additional D relay would be necessary for discrimination in this latter case.