GB693588A - Improvements in or relating to automatic telephone and like selecting systems - Google Patents

Abstract

693,588. Automatic exchange systems. REUMERMAN, T., and HELMIG, W. H. T. Aug. 18, 1948, No. 27548/50. Divided out of 693,554, [Group XIX]. Class 40 (iv). [Also in Group XIX] A connection is not completed until an extra digit R is dialled to check that the wanted number ABCDE has been correctly dialled. The checking digit R is the remainder on dividing ABCDE by 11. The digit 0 is regarded as 10 for the purpose of determining R. In one arrangement, an individual ten-point switch CS, Fig. 1, is connected in the line between the station T2 (No. 29047-6) and the final selectors C. The sixth contacts of the switch are connected to the station and the remaining contacts to a slow-to-operate relay R. If the number dialled at T1 does not correspond to the checking digit, R operates, connects 'wrong number tone from G and is followed after a delay, by relay D which releases the connection. The home position hc of the switch is used to mark the checking digit 0. In an arrangement employing register translators - TR, Fig. 3, a checking switch CH is connected in parallel with each translator. The checking switch is stepped in opposite directions by alternate digits and ends up in its home position hc if both the wanted number and the checking digit have been dialled correctly. When a call is originated at T1, a free translator is selected by a preselector P, relay IR operates and is followed by V which remains operated for the duration of the call. The dialled digits are repeated by IR to the translator TR over switch wiper SW1 and to driving magnets M2, M3 of the switch CH over wiper SW2. The magnets M2, M3 step the switch CH alternately in opposite directions and are connected to alternate switch contacts. The switch SW counts the digits under the control of a dialling relay U and a magnet M1. The translator transmits three digits over switch SX to operate selectors S1, S2, C. The third digit is not transmitted until the five digits and the checking digit are correctly dialled. Relay F is then operated over the wiper of CH in its home position, relay X having been operated after receipt of the fifth digit. With F operated, a direct circuit is completed through contact f2 to the called station. If the number has been wrongly dialled and CH is not in its home position when X operates, relay R operates to transmit wrong number tone and to release the connection as before by operating relay D. Relays Y, Z then interact to home the switch CH. Specification 693,586 is referred to.