Patent GB-687747-A (GB)
Title: Improvements in or relating to electrical escapement circuits for use in automatic telephone-exchange and like systems for numerically positioning group selectors
IPC: H04Q3/42
Filed: 1950-11-17
Abstract: 687,747. Automatic exchange systems. PHILIPS ELECTRICAL INDUSTRIES, Ltd. Nov. 17, 1950 [Nov. 22, 1949], No. 28155/50. Class 40 (iv). A single-motion group selector is set numerically by means of a local circuit of the " electrical escapement " type described below under the control of a series of impulses emitted by a register-controller, the emission of any control impulse after the first being delayed until the register-controller receives a signal which is sent by the selector after it has stopped at the first outlet of a numerical group upon reception of a complete control impulse. In the " electrical escapement " a test bank of the selector comprises two sets of contacts, each set being commoned and the contacts of the two sets being arranged alternately. One set has a " stop " marking and the other a " start " marking, and the markings are interchanged at suitable intervals so that the selector is stepped. Any further contacts of the bank have a " start " marking, at least during the numerical setting. As shown, a single-motion group selector GK has an " escapement " bank c in which the " start " marking is earth and the " stop " marking is absence of earth. The number of impulses to be sent is registered in a counting circuit TS in a register-controller REG and the group selector GK is seized, whereupon a relay TU releases to bring up relays B and I. This initiates the first impulse which is counted by TS, and a relay O operates to apply earth (" start " marking) to the rest contact N of the bank c, thereby energizing a " governor " relay Y and rotary magnet D which moves the selector to the next contact H. The operation of Y releases the impulsing relay I, ending the first impulse and releasing relay O which now applies earth to contact H in bank c so that rotary magnet D is re-energized and moves the selector to U11, the first outlet of the first numerical group. This is not earthed, and D and Y are de-energized. The release of Y allows I to re-operate and initiate the second impulse, whereupon O, D and Y are energized as before and the selector moves towards contacts U15, the intervening outlets being earthed in bank c. The second impulse ends with the release of I followed by O, causing the selector to move on to U21, the first outlet of the second group. Here D and Y are released as at U11. The selector continues to step in this way until the required number of impulses, as registered in the counting circuit TS, has been sent, whereupon relay TU pulls up to disconnect the impulsing relay I. If the selector has reached the first outlet of the wanted group, the release of relay Y is now followed by the release of relay B which connects rotary magnet D and relay Y to test wiper Td instead of Tc. If, however, the selector has not reached the first outlet of the wanted group when relay TU pulls up, an auxiliary governor relay Q is energized and holds independently of the subsequent condition of TU so that the impulsing relay I remains disconnected until the selector is ready to receive the next train of impulses. When the selector reaches the first outlet of the wanted group, relays Y and B release, followed slowly by Q, while D and Y are re-energized if the first outlet is engaged, indicated by earth in contact bank d. The selector hunts for an idle outlet, which exhibits no earth in bank d so that relay Y releases and restores the connection to the impulsing relay I which sends the next impulsetrain to the following switching stage to which the group selector is connected by the operation of a relay T (not shown).