Patent GB-304813-A (GB)
Title: Improvements in automatic or semi-automatic telephone systems
IPC: H04Q3/58
Filed: 1927-10-26
Abstract: 304,813. Standard Telephones & Cables, Ltd., (Deakin, G., Polinkowsky, L., and Hatton, W.). Oct. 26; 1927. Automatic and semi-automatic exchange system. -Main and satellite exchange are connected by two-wire two-way junctions comprising linefinders at each end operated in synchronism by impulsing means provided, at each end, and used at the calling end. The relay Epr (Spr) at the calling end interacts with a relay Ep'r (Sp<1>r) and the magnet Esm (Ssm) to step the switch LF (LF<1>),. while the relay Sbr (Ebr) at the called end repeats the impulses to the other switch magnet. Relays Ear, Sar are normally energized in a charging circuit for the 24-volt satellite battery from the 48-volt main battery, but this is cut when the calling line is found. The satellite subscriber is rung from. the main exchange, a ringing relay at the satellite responding thereto and extending the ringing circuit to the subscriber; the relay is disconnected during conversation but re-connected on release in case of re-ringing. The ringing relay is prevented from operating in a call to the main exchange. The switches LF, LF<1> of the several junctions between the exchanges have chain circuits over the x contacts of the magnets Esm, and the said contacts do not close until the switch has stepped over certain blank contacts, so that if the first switch has a defective test relay Etr and steps over the calling line, the second switch will find. A number of switches at each end having staggered home positions may be stepped by common impulsing means to find the calling line. Call from main exchange to satellite. When the final selector has operated, ground is placed on the selected C-wire to operate relay Twr, Fig. 1. Relays Emr, Eor pull up in turn, and the outgoing impulsing circuit is formed [battery, Etr a, Epr, Ep<1>r alpha, Eor d, Egr e, b wire, Scr e, Sor f, Sbr, Sbr a, Sar b, ground] energizing relays Epr, Sbr. The operation at the main exchange end will be dealt with first. Relay Efr energizes in series with magnet Esm which is short-circuited at present. Relays Eir, Ef<1>r energize over Efr r a, the former allowing Esm to operate, and closing a locking circuit for Eor so that the latter holds up although relay Ebr now energizes. Esm removes a short from relay Ep'r, which deenergizes Epr to release Esm; Ep'r is in turn released to allow Epr, Esm to re-energize, when Ep<1>r again operates. The line-finder LF is thus stepped ; and the de-energization of relay Sbr in the pulsing circuit synchronously operates magnet Ssm, Fig. 2, to step the finder LF'. When LF finds the calling line test relay Etr operates over the d brush, de-energizing Epr, Efr, Eir, Ef<1>r, Eor.. turn, and energizing relay Egr. The charging circuit is opened at Egr a de-energizing Ear, Sar, and the line is busied from earth at Egr @. Relay Ekr operates so that ringing current energizes relay Ejr. Ecr energizes and locks up, releasing Ekr, Ejr and connecting up thÀ junction so that ringing current is sent to the satellite. At the satellite when Sbr is energized in the pulsing circuit, relays Sfr, Se<1>r, Sir, Ser, Shr operate in turn, the last locking up. The impulses transmitted to Sbr operate magnet Ssm over Sbr a. When the pulsing circuit is finally cut out, relays Sbr, Sar Sfr, Se<1>r, Sir release in turn, and relays Scr Sdr energize to form a holding circuit for Ser before it releases, to swich the junction through, and to energize the subscriber's cut-off relay Cor. Ringing current now operates ringing Sjr, so that relays Syr, kcr pull up and the wanted line is rung. [Junction a-wire, Rcr f. Scr b, wanted line Ser c, Rcr @, Sjr, Sgr, c, Scr, d, junction b-wire,]. On reply, Sjr releases, due to the operation of the main exchange ring-trip relay, and releases Syr, Rcr'. Feed relays Ssr, Ss<1>r are now connected up, and relay Sgr then energizes to complete the talking circuit, and to remove a short around Slr which energizes. Sdr is short-circuited over Ssr a, St<1>r a, Sxr a. Release (a) by satellite subscriber. Ssr, Ss<1>r release, de-energizing Sgr, Slr, Ser, Scr in turn, so that Cor releases to free the wanted subscriber's line. LF<1> homes and releasee Shr at Ssm y. The calling line is not released. (b) By calling subscriber. Twr releases and Emr, Etr, Ecr. Egr release in turn. Ecr opens the junction to release Slr, Fig. 2, so that the called subscriber's line is released as before, and relays Ear. Sar pull up in the charging circuit. LF is now hcmed over its contacts z, whereupon Ehr releases. Call to main exchange. Subscriber's line relay Lr energizes relay Smr, which energizes Sor to form an impulsing circuit in which Spr, Ebr pull up. Sfr energizes in series with short-circuited magnet Ssm and Se'r, Sir then energize in parallel. Scr, Shr energize. The magnet Ssm and relays Sp<1>r, Spr then interact similarly to Esm. Ep<1>r, Epr to step the switches to the required contacts, when relay Str energizes over brush d<1> and opens the pulsing circuit. Relays St<1>r. Sxr. Syr pull up, while Ear, Sar release. Sxr locks up and releases Sir. Relay Scr energizes over Sar a, Ssr. Ss<1>r pull up over the subscriber's loop, and Cor operates over brush c<1>. LR, Str, St<1>r. Smr, Sor release, and Syr de-energizes allowing Sgr to pull up. Relay Slr now operates over the junction. When Ebr pulled up in the main exchange, relays Efr, Eir, Ef<1>r, Ehr energize in turn, and Ebr responds to the impulses at the satellite to step LF in synchronism with LF<1>. Ear releases when LF<1> finds and Edr operates to earth the c-terminal of LF so that the magnets of all idle line-finders ILF are operated over lead FS and one of them extends the connection to a register, when ground on ILF c energizes Twr, so that Etr pulls up, and releases Edr. Relays Ecr, Egr energize in turn, releasing Ebr, Efr, Esm, Eir Ef'r, and the junction is now connected through to the register. The satellite subscriber receives dialling tone and each dialled impulse de-energizes Ssr, Ss<1>r. Syr energizes throughout each digit to release Syr, which shorts Slr and closes a low-resistance bridge across the junction over Ssr a so that each impulse is repeated to the register. If the main exchange were manual, the energization of Edr would light a signal to call an operator who would set up the connection. Release (a) by satellite subscriber. Relays Ssr, Ss<1>r, Sgr, Ser, Sxr, Slr, Ser, de-energize in turn, but Sdr is energized over the junction [resistance R, Rcr d, Sgr e, Sxr, e, Sdr, Scr d, b-wire], maintaining Ser energized. When the main exchange subscrib:r hangs up, Sdr, Ser, Scr release in turn and LF homes over its own contacts z. (b) by main exchange subscriber Twr, Etr, Ecr, Egr release in turn, opening the junction to release Slr so that the satellite returns to normal as described before.