Patent GB-805326-A (GB)
Title: Improvements relating to automatic telephone exchange systems
Inventor: FLOOD JOHN EDWARD
IPC: H04Q3/42
Filed: 1955-11-24
Abstract: 805,326. Automatic exchange systems. SIEMENS EDISON SWAN Ltd. Nov. 20, 1956 [Nov. 24, 1955], No. 33739/55. Class 40 (4) and 40 (9). A register-sender has access to a translator, which may be in the form of a magnetic drum, the register-sender operating switches according to the code to be translated to gain access to the address in the translator at which the translation is stored. First embodiment, Fig. 1. Translation digits stored in serial form. The magnetic drum has 100 tracks, each track having ten sectors, each sector holding first and second choice translations for one set of code digits. The translator receives code digits from a register over three groups of leads L1-L3, the values of the digits being indicated in a 2 out of 5 code. Each combination of leads in a group is connected to one of ten gates such as GA which opens when both leads are marked to energize the associated relay RA. Thus for each code combination dialled one of the relays in each set RA, RB, RC pulls up. Relays RA and RB select one of a hundred reading heads H, each head being associated with a track bearing the translations of ten combinations of code digits. As the drum rotates these translations are fed to a gate G1 which is opened on alternate revolutions of the drum to feed gate G2. Relay RC applies one of ten pulse trains TP(1)-TP(10), the pulses in each train lasting for one-tenth of a drum revolution, to open gate G2 while that sector of the track is being read. According to when the register is ready to receive the first, second, and so on translation digit so it signals over leads L4 to energize a corresponding relay RD which applies the corresponding one of seven pulse trains WP(1)- WP(7) to gate G4. The register also marks lead L5 or L6 according to whether the first or second choice of translation is required to open gate G4 at the time of pulse CP 1 or CP2 as the case may be whereby the desired translation digit of the first or second choice is passed by gate G3 to each of five gates GT opened cyclically in turn. The two gates GT which receive the binary digit 1 operate corresponding trigger circuits T which mark associated leads in group L7 leading to the register. The trigger circuits T are reset at the beginning of each rotation of the drum. Second embodiment, Fig. 2. Translation digits stored in parallel form. In this case thirty tracks each holding 1,000 digits are allotted to the address. The code digits from the register operate corresponding relays RA, RB, RC as before to select corresponding tracks AH1-AH3. When outputs from the associated reading heads coincide gate G7 opens. The corresponding alternative translations are read in 2 out of 5 code at each position of the drum by heads TH1-TH5 and TH1<SP>1</SP>-TH5<SP>1</SP>. Choice of the first or second translation is made by operation of relay 1CR or 2CR and choice of the particular digit required by one of seven relays RD. The required translation digit is then applied to trigger circuits T1-T5 as in the first embodiment. Selection of reading head by means of saturable transformers, Fig. 6. The ten reading heads in a group feed input windings WI of ten transformers 1-10 which are normally biased to saturation in the opposite direction by windings WB. When a code digit is applied in two-out-of-five code to leads L saturation is overcome in only one of the transformers 1-10 so that it produces an output on its winding WO corresponding to the information read by its associated reading head. Details. An n-gate may comprise a resistor and n-1 rectifiers in parallel connected to the grid of a valve (Fig. 4, not shown). Alternatively it may comprise n rectifiers in parallel connected to the base of a transistor (Fig. 4a, not shown). Valve and transistor trigger circuits are described (Figs. 5 and 5a, not shown). The translator may be connected cyclically to a number of registers or only to those registers requiring the services of a translator.