Patent GB-826040-A (GB)
Title: Improvements in or relating to telegraph communication systems
IPC: H04L12/14
Filed: 1956-09-13
Abstract: 826,040. Telegraph exchange systems. COMPAGNIE INDUSTRIELLE DES TELEPHONES. Sept. 13, 1956 [Sept. 16, 1955], No. 28015/56. Class 40 (3). In a telegraph system using the 5-unit code, the operation of call-charging apparatus is rendered dependent on the first character of the preamble code which is employed after the connection has been established. If the first character of the code is carriage-return, figure-shift, or line-feed, as denoted by diagrams II, III, IV of Fig. 1, the call is not charged, but the lettershift signal, diagram I, at the beginning of the preamble, results in the charging of the call. On the establishment of a call connection relay TG operates, connecting at contact TG1 ground to several circuits and in the rest condition of the arrangement relays 6, 3 and 2 are operated. When, for example, the preamble code commences with the signal II, the start element energizes relay 5 and the lower winding of relay 4 is short-circuited. These conditions persist during elements 1, 2, 3 and the positive element 4 operates relay 4 over its lower winding whilst the circuit of relay 6 is opened at contact 45, but the relay has a delay period of 60 msecs. and does not release until the stop element. During the fifth element, a circuit is completed for the upper winding of relay 5 which releases, and during the stop element relay 6 releases so that at the end of signal II relay 4 is energized and relays 5, 6 are de-energized. Similarly, at the end of the signals III and IV, relays 5, 6 will be de-energized and relay 4 energized. In response to the signal I, relay 5 energizes during the start element, relay 4 operates in response to the first element and relay 6 releases at the beginning of the fourth element so that at the end of this signal relay 6 is released, but relays 4, 5 are operated. The operating circuit of the second winding of relay 2 is opened at contact 61 of relay 6 but reception of marking and spacing elements at contacts R, T engaged by armature A of relay 1 close circuits to capacitors C3, C4 to provide current through the lower winding of relay 2, the resistors r6, r7 being of such value in combination with capacitor C3 or C4 that the relay will hold for a period corresponding to five code elements plus the stop element so that if a spurious start element simulated the signal I, the relay 2 would release and effect the release of relays 4, 5 with the result that the arrangement would be restored to normal. With TG1 operated, a relay 3 is operated over released contacts 41, 51 and a capacitor C1 combined with resistors r1, r2, r3 provides for relay 3 a release period slightly less than that necessary for the transmission of the twenty characters of the preamble code. When relay 3 releases, earth is applied to conductor q over contact 32 and contact 47 of operated relay 4. If the call is not to be charged, relay 5 is in released condition and earth is also applied over contacts 46, 54 to conductor p. If the call is to be charged, the operated contact 54 prevents earth from being applied to conductor p and the charging apparatus is brought into operation.