Patent GB-254116-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1925-07-24
Abstract: 254,116. Pollak, J. E., (Siemens & Halske Akt.-Ges.). July 24, 1925. Automatic and semi-automatic exchange systems; metering. - A small automatic rural exchange is provided with rotary connectors for seizing an idle trunk to the nearest manual exchange in response to a particular dialled number, and the connection is then completed by an operator. In the case of a local call, metering is effected automatically upon release, but in the case of a trunk call, metering according to the zone of the called party is controlled by the operator, who may employ a special set of keys or her impulse dial for the purpose. In the embodiment described, the rural exchange (Fig. 1) comprises only line switches and connectors, and the trunks to the manual exchange terminate either in plugs (Fig. 2) or jacks (Fig. 3). In the case of a trunk call, the feed relays at the connector are cut out, and these relays are employed to repeat back metering im. pulses. In the arrangements described, ground metering impulses are sent over the trunk line, but loop impulses may also be used. Local call. Upon seizure by the line switch VW of the connector LW, line relays A1, B1 energize, and at contact 13 remove a short-circuit from relay VI so that it operates over the test wire, and locks. Dialled impulses are repeated to the vertical magnet HI at contact 11, changeover relay V2 (I) being energized during the train over back contact 13, and then falling back to connect up relay F(1) over side switch contact VI and off-normal contact 24. Magnet St advances the side switch to the second position and short-circuits relay F(1) which relapses. Impulses are now repeated to the rotary magnet D1 and the side switch is moved into the 3rd position in a similar manner. If the wanted line is free, test relay Y2(I) energizes over contact IV in series with cut-off relav T1<1>, and locks over winding Y2(II). Marginal relay P is connected to the test wiper to mark the called line busy, but it does not operate owing to the high resistance of relay T1<1>. The side switch is advanced by relay F(1) to the 5th position, in which an initial ringing current is completed over side switch contacts III, IV. An interrupter 138 after an interval sends an impulse over contact VII to relay F(1) to move the side switch into the 6th position, in which normal ringing current is sent over ring cut-off relay F(II), which energizes upon reply of the called party. The side switch is moved into the 7th position, and the speaking leads are extended over contacts III, IV until the 11th position is reached. In the 7th position, the called party receives feed current over relays Y1 and Y2(I), and the former relay connects up relay F(1) to move the side switch into the 8th or talking position. Release and metering. When the called party hangs up, the feed relays fall back and relay F(I) advances the side switch to the 9th position, where it remains until the calling party hangs up. When this occurs, relays A1, B1, V1 fall back, and relay V2(I), being no longer shortcircuited at contact 13, energizes, connecting up relay F(1) to move the side switch into the 11th position, in which the busv mark is removed from the called line. Relay V2(I) relapses after an interval during which a metering impulse is sent back over the test wire to the meter Z. The release magnet M1 operates to restore the connector, and, when the normal position is reached, relav F(1) advances the side switch to the 1st position. Trunk call: first arrangement, Fig. 2. In response to the dialled digits, the wipers of the connector LW are set on the first line of a trunk group, and in this position cam contacts 32 are closed, so that when relav V2(I) falls back in the 3rd nosition of the side switch, a circuit is completed for relays V2(II) and Y1(I) over contact TV. If the first line of the group is engaged. test relay Y2(I) does not operate, and relay Y1(I) connects up the rotary magnet D1 again over contact II. The rotary magnet con- 1 trols a short-circuit for relay Y1 (I) over contact III, so that interaction continues until an idle line is found. Test relay Y2(I) then energizes in series with relay C1(I), and disconnects relays V2(II) and Y1(I). Marginal relay P is con. nected to the test wiper and operates, extending the speaking wires and preventing advance of the side switch when relay V2(II) falls back. Relay P1 energizes, locks over the test wirc and disconnects feed relays A1, B1. Relay VI is short-circuited and relapses. Relay C1(I) upon energization connects up sluggish relay HR, while line relay A2 energizes and locks relay C1(II). Before relay HR pulls up, an impulse is sent over wire 66 to energize relay S, Fig. 2, which locks and lights calling lamp AL. The operator throws her speaking key 72, releasing relay S, and completes the desired connection by inserting plug VSt in which the trunk line terminates in jack VK1. Sleeve relay B2 operates, Release and metering up the operator. When the calling party hangs up, feed relay A2 falls back, closing a circuit over wire 77 for relays G, R2. Calling lamp AL, which also serves as a clearing lamp, lights, and relay P relapses, con. necting relays A1, B1 to the line wipers, so that relay A1 energizes, and prevents operation of the release magnet M1 in the 4th position of the side switch, to which it is now advanced by the energization of relay F(1). The operator throws her speaking key 72 to connect up the metering equipment, providing a locking circuit for relay R2 independent of relay B2, so that plug VSt may be removed. Relay P2 energizes and locks over its low resistance winding to prevent any other line being connected to the metering equipment. Contacts 100 are closed when any metering key ZT is operated, energizing relay Q which locks. Relay J1 energizes, and transmits a metering impulse over wire 66 to relay ZR, which controls relay B1 whereby relay P1 is short-circuited and an impulse of increased current sent over contacts 49, 119 and the test wire to the meter Z. Sluggish relay J2 energizes and disconnects relay J1 to send an impulse to the magnet D2 to advance the switch ZS one step. Relay J2 relapses, and this action is repeated. impulses being sent alternately to relay ZR and the magnet D2, until the switch ZS reaches the terminal grounded by the operated key ZT, whereupon relay Q is short-circuited, opening the metering circuit and closing a restoring cir. cuit for the magnet D2, which now interacts with relay J1 only. Relay J1 lights lamp AL as each metering impulse is transmitted. The operator clears by restoring her speaking kev 72, releasing relays P2, R2, G. Relay A1 therefore falls back and connects up the release magnet M1 which removes holding ground from the test wire. When the normal position is reached, relay F(1) energizes successively to move the side switch from the 4th to the 1st position. Trunk call; second arrangement, Fig. 3. Connection is made as before to an idle trunk line which terminates in jack Kli1, and the calling impulse sent over wire 66 operates drop signal Kla. The operator completes the connection by means of a cord circuit Stp1, Stp2 over auto. matic switches, for example at another exchange, 1 which are controlled through a dialling plug Stp3 and a dialling jack Wkl. When the called party replies, relay S energizes and connects up clearing drop signal Skl2. Drop signal Ela is now connected to wire 77 to act as a clearing signal. In order to effect metering, the operator inserts her dialling plug Stp3 in jack Zkl, and operates her dial to send the necessary number of impulses over 66 to control ZR, as is done automatically by the metering equipment of Fig. 2. The operator clears by removing plug Stp1.