Patent GB-747563-A (GB)
Title: Circuit arrangement for telecommunication installations especially telephone installations
IPC: H04Q3/42
Filed: 1953-04-08
Abstract: 747,563. Automatic exchange systems. SIEMENS & HALSKE AKT.-GES. April 8, 1953 [April 8, 1952], No. 9542/53. Class 40 (4). Different states of a selected line are characterized by signals which control different switching operations through an arrangement which determines whether the duration of a current impulse or of a pause between two impulses is greater than a predetermined time duration and which is brought into operative condition only by a current impulse of which the duration is at least substantially equal to the said predetermined time duration of a current impulse. The embodiment shown comprises a waiting arrangement which periodically tries to establish a wanted connection and recalls the calling party when it finds the wanted line free. Call from subscriber Tn. A preselector VW seizes a free group selector GW over wire c, bringing up relays A and C in the waiting arrangement WE. Dial impulses are repeated by relay A to the seized group selector GW and also to a storage arrangement Sp in which relays S and V are energized. If the wanted line is free, the call proceeds in normal fashion. Wanted line busy; initiation of waiting condition. The calling subscriber Tn briefly operates a key TA to energize a differential relay X followed by relays O and E. On the release of key TA, relay X falls back and brings up a relay D which releases the group selector GW and subsequent equipment while holding the preselector VW. When the calling subscriber Tn hangs up, relays A and O are released, once more seizing a group selector, and relays C1, Y, N, G, and W are energized. Waiting arrangement repeats call. The storage arrangement Sp temporarily energizes winding (II) of relay U which then holds on its winding (I). Relay J repeats the stored dial impulses to the group selector. When all the impulses have been sent, relay S falls back and relay P is energized, releasing relay U to bring up a relay L followed by L1. A storage control relay V falls off slowly. The speech path is now connected to a signal receiver SE in which a relay I is arranged to operate during the reception of tone current and to release during the pauses. The first operation of I in response to a signal causes relay Y to release with a delay which is such that the brief operation of I by switching clicks or similar noises does not release Y. The relapse of Y brings about the operation of a relay T which makes the condition of relays G and N, previously energized, depend upon the condition of relay I, i.e. upon the nature of the signals received. The signals employed are indicated in Fig. 2. The engaged signal BZ consists of alternate tone current impulses lasting 200 ms. each and pauses of about 400 ms. The free signal FZ comprises 1 sec. tone and 9 secs. pause, and the dialling signal WZ, denoting that a previously-engaged switching stage has become free, comprises 200 ms. tone, 300 ms. pause, 700 ms. tone, and 800 ms. pause. The relays G and N are arranged so that the reception of tone current tends to release G and a pause tends to release N, but the release delay of G is sufficient to bridge a 200 ms. tone while the delay of N will bridge a 400 ms. pause. Wanted line again found busy. The engaged signal BZ leaves G and N both operated, and the operation of relay T brings about the delayed release of relay L which releases the group selector and subsequent equipment. Relay C1 thereupon falls back, followed by N, G and W. After a predetermined interval a time switch ZS releases relay L1, and the call is repeated periodically in this way. Wanted line found free. Reception of either the free signal FZ or the dialling signal WZ causes either G or N to release, followed by relay W which brings up relay R to send ringing current to the calling subscriber Tn and to release relays L and L1. When Tn lifts his receiver, differeritial relay X is operated, releasing relays E and R to disconnect the ringing current and bring up relay A followed by M which completes the connection. The relapse of E removes a short circuit from winding (II) of differential relay X which thereupon falls back, followed by all the other energized relays except M which holds on its winding (I) until subscriber Tn hangs up.