Patent GB-191303431-A (GB)
Title: Improved Circuit Arrangements for Automatic or Semi-automatic Telephone Systems in which there are Several Lines to a Station or Group of Stations.
Filed: 1913-02-10
Granted: 1914-03-10
Abstract: 3431. Siemens & Halske Akt.-Ges. Feb. 9, 1912, [Convention date]. Automatic and semi - automatic exchange systems.-Relates to the establishment of trunk or other preferred calls in private branch exchange systems connected to the main exchange by several lines having equal exchange facilities, particularly in the case where all the lines are engaged either in preferred or ordinary calls. Three methods of establishing such preferred calls are described as applied to three known methods of extending a call over the first idle line to a private branch exchange, these three methods being shown in Figs. 1, 2, and 3, respectively. First system, Figs. 1 and 1A. In this system, it is assumed that if all the lines to the private branch exchange are in use, the connector LW, Fig. 1, is arrested upon the last set of contacts 18, 19, 20, connected to a special intermediate non-numerical selector ZW, which controls the establishment of the preferred connexion. Of the five subscribers' lines only the test contacts 1, 2, 3, 4, 5, are shown in Fig. 1, and of these the contacts 1, 2 are shown directly earthed over the test arms 6, 7 of connectors making preferred calls, the contacts 3, 4 are earthed through resistances 50, 51 over the test arms 8, 9 of connectors making ordinary calls, while the contact 5 of a line supposed to be engaged in an out-going call, is shown earthed through a resistance 10. The speaking and test contacts of the five lines are multipled to the contacts of the connector LW, and of the intermediate selector. If the connector LW, controlled, say, by a trunk operator, finds all the five lines engaged, it comes to rest on the contacts 18, 19, 20 of the special selector ZW, which then rotates to find a line engaged in a non-preferred call. By the co-operation of the subscriber, this line may be freed for use by the pending call. The Specification as open to inspection under Section 91 (3) (a) states that the subscriber can effect the release of any one of his lines and that the call may be set up over such line, either by a second connector over a second line, or by causing the intermediate selector ZW to continue its hunting movement to find the freed line. The contacts of the lines 1 ... 5 may be repeated in the bank of the selector ZW, so that in case the called subscriber engaged in a non-preferred call does not immediately release the connexion, a second test may be made when the wiper 34 reaches the multiple of this line. This subject-matter does not appear in the Specification as accepted. Operation of connector LW, Fig. 1A, in making connexion with an idle line to a private branch exchange. During the transmission of the selecting-impulses, the relay X is energized, and the tens impulses are repeated by the relay A to the vertical magnet H over contact x2. The relay X then de-energizes the magnet S, which moves the side switch into its second position, in which the units impulses are repeated to the magnet D. The connector is thus set on the first line of the wanted subscriber, and a circuit is closed for relays U, P<1> over wiper 21' and a resistance w1, of such a value that the relay P<1> is energized, but not the relay U. The relay P', (1) by closing contact p<1>2 shunts a resistance w round the relay X, so as to energize this to lock the side-switch in its second position, (2) connects the test relay Y over contact p<1>3 and arm s8 to the test wiper 20<1>, and (3) completes at p<1>1 the circuit of the magnet D, which rotates the connector until an idle line is found, or until it reaches the last set of contacts. If an idle line is found, the relay Y is energized, and (1) disconnects the rotary magnet at y3, and (2) opens the shunt round the relay X, so that the magnet S moves the side switch into its third position and thence into its fourth position and fifth position. Supply of ringing current, Fig. 1A. In the transient fourth position, the relay Y is disconnected from the test lead, and the ringing- relay L earthed over arm s2. In the fifth position, the relay L is periodically energized over a time switch w4. When the called subscriber replies, the relay Y is energized over arm s12, wiper 19<1>, the called line, wiper 18<1>, coil D2, and battery. The relay Y cuts off the ringing- relay, and by closing contact y1 moves the sideswitch into its sixth or talking position. During the ringing period, the armature l of relay L connects a special signal to the calling line. Normal release, Fig. 1A. When either subscriber hangs up, the magnet S is energized over contact b2 or y1 and moves the side-switch into its seventh position, thus energizing a relay Q in series with the test relay of the group selector. The relay Q energizes the magnet S and when the group selector is released, as described in Specification 6654/10, the magnet S moves the side-switch into its eighth position in which the relay A is energized over arm s6 and magnet S. The relays B, X are also energized. If or when the called subscriber hangs up, the relay Y closes the circuit of the side-switch release magnet N over arm s10, thus returning the side-switch to normal and energizing the connector release magnet M. Establishment of preferred call, Figs. 1 and 1A. If all the lines to the private branch exchange are in use, the connector rotates as before until its wipers engage the last set of terminals 18, 19, 20, 21 connected to the special selector ZW, the terminal 21 of which is directly earthed so that the relay U is energized and opens at contact u3 the shunt round the relay X, so that the magnet S moves the sideswitch into its third position, where it remains since the relay Y is de-energized. The trunk operator, receiving no indication that an idle line has been found, interrupts the a-lead and connects the battery to the b-lead, thereby energizing the relay X, which, by closing contact x4, earths the outgoing a-lead, energizing a relay 24, Fig. 1, and thus exciting a relay 26, which locks up over contact 27 and maintains at contact 28 the circuit of the operating magnet 29 of the selector ZW, which rotates the wipers until the test relay 32 is energized. As long as the wiper 34 engages the terminals of lines, such as 1, 2, used for preferred calls, the relay 32 is short-circuited, but as soon as it reaches lines not so engaged, it is energized in parallel with the resistance 50 or 51, thus arresting the selector ZW, and extending the calling line over contacts 37, 38 to the found line. By the co-operation of the subscriber, this line is freed for use by the pending call. The trunk operator again interrupts the a-lead, and applies battery to the b-lead, thus energizing the relay X and magnet S, so that the sideswitch moves into its sixth position, and the outgoing b-lead is earthed over arm s7 and contact x4, thereby energizing a relay 23, Fig. 1, which disconnects the test relay 32, and connects a relay 33 to the test wiper 34. The relay 33 (1) open-circuits the motor magnet 29 at contact 31, (2) short-circuits the condensers 48, 49 at contacts 43, 47, (3) disconnects the relays 23, 24 at contacts 44, 46, (4) locks up over contacts 45, 41 and relays 26, and (5) directly earths the test wiper at contact 42, so that the line tests busy to other preferred calls. When the trunk operator disconnects the line, the relays A, B, bring about the release of the connector in the manner previously described, the direct grounding of the test lead c over contacts u7, b3, Fig. 1A, releasing relay 33, Fig. 1, which returns the selector ZW to normal. Second system, Fig. 2. In this system it is assumed that the test contacts of all the lines, except the last, have a positive engaged potential, while the last line is provided with a negative potential at its engaged characteristic. Instead of using different kinds of potential, a special test arm can be provided in known manner for the last line. Fig. 2 shows the test contacts 1 ... 5 of five lines, of which contact 1 is shown earthed through a low resistance 6, over the test arm of a connector making a preferred call, contacts 2, 3, 5 are earthed through higher resistances 7, 8, 10 of ordinary connectors, and contact 4 of a line engaged in an outgoing call is earthed through a resistance 9. The cut-off relays 11 ... 14 of the preliminary selectors of lines 1 ... 4 are connected through a resistance 16 to the positive pole of a battery, while the relay 15 of the last line is connected through a resistance 17 to the negative pole of a battery. The cutoff relays 11 ... 15 control pairs of contacts 36 ... 45, so that when all the lines are in use, the resistances 16, 17 are short-circuited. The connector shown in Fig. 2 is used for both ordinary and preferred calls. Operation of connector, Fig. 2, for ordinary calls. After the wipers have been brought to the terminals of the wanted line by the vertical and rotary magnets H, D, in the usual way, the side-switch passes into its third position, thus energizing a relay 18, which completes at contact 20 a circuit for the test relay P from ground over contact 20, sensitive polarized relay 26, winding 24, contact 23, and wiper 47. If the wanted line is free, the relay P is energized, opens the circuit of relay 18, and connects it to the outgoing a-lead. The ringing relay is energized over contacts p6, 54, and when the called subscriber answers is disconnected by the energizing of relay 18. If the selected line is the first of several lines to the same subscriber, a relay P<1> is energized over a fourth wiper, and in the third position of the side-switch closes a fresh circuit for the rotary magnet D over arm s7 and contacts p1, p<1>, 28, 22, the relay 26 being energized whether the tested line is busy or idle. When a free line is reached, the relay P is energized, and arrests the connector, and rings up the selected line as described above. If all the lines are busy, the wipers reach the last set of contacts, th