US1900911A - Telephone system - Google Patents

Description

March 14, 1933. D, A. CHRISTIAN 1,900,911

TELEPHONE SYSTEM Filed Nov. 17, 1930 10 Sheets-Sheet l InusnZnr David Hdam Cm arm.

March 14, 1933, D. A. CHRISTIAN TELEPHONE SYSTEM Filed NOV. 17, 1950 10 Sheets-Sheet 2 ITL'LI'ETL :11" David Edam Cm March 14, 1933. D. A. CHRISTIAN TELEPHONE SYSTEM Filed Nov. 17, 1930 10 Sheets-Sheet 3 1111A ML M m w /u W M DFM olfm

In'U'En U1" Dauid'fidam Chm March 14, 1933. D. A. CHRISTIAN 1,900,911

TELEPHONE SYSTEM Filed Nov. 1'7, 1930 10 Sheets-Sheet 4 dbl m4 :51 am I 3 MS! 1M J 5 56.70 A3 a B 9* l gl David 5:1 am CHEW March 14, 1933. D.- A. CHRISTIAN TELEPHONE SYSTEM Filed Nov. 17,

1930 10 Sheets-Sheet 5 ltLLL ii l nueniur Dauid? am Z'LT'IEZIETZ March 1933. D. A. CHRISTIAN 1,900,911

TELEPHONE SYSTEM Filed Nov. 17. 1930 10 h ets-she 6 Inventor David Edam Chi 157E March 1933- D. A. CHRISTIAN 1,900,911

TELEPHONE SYSTEM Filed NOV. 17, 1950 10 Sheets-Sheet 7 David Edam Chi-'15 1511 March 14, 1933. [1 cH s N 1,906,911

TELEPHONE SYSTEM Filed Nov. 17, 1950 10 Sheets-$heet 8 n, 0% g 2 i $0 FIG. 9a.

Ive-m? David Edam Em March 14, 1933. D cH s g L900,911

TELEPHONE SYSTEM Filed Nov. 1'7, 1950 10 Sheets-Sheet 9 I w "2, ijilllllli% m: m t) TD a d2 "2 VM RM g a 1m DBL/i13 Edam Chm March 14, 1933,

Filed Nov. 17

10 Sheets-Sheet 10 K4 3 If A sm L scz"'; J6 V 5033; H/ TF P k5 fl k3 w \r \q/ 1 M 4 t? v 1 K (1) TF HG. lOa.

Patented Mar. 14, 1933 ITED stares PATENT OFFICE 'DAVID ADAM CHRISTIAN, OF LONDON, ENGLAND, ASSIGNOR TO SIEMENS BROTHERS &

COMPANY LIMITED, OF LONDON, ENGLAND I TELEPHONE SYSTEM Application filed November 17, 1930, Serial No. 496,145, and in Great Britain November 23, 1929.

The present invention relates to rotary switches of the kind used in automatic telephone systems.

In switches of this kind a number of contacts are formedin an arcuate bank at the centre of which is a spindle carrying arms or wipers which on rotation make contact with the bank contacts.

It is usual for the bank to subtend an angle of 120 or 180 and to avoid rotating the wipers and collector rings, a' set of: wipers is connected to a link or connecting circuit.

In the present invention a switch is provided with a plurality of wipers adapted to wipe over the same bank contacts in succession, the several wipers being associated with different brushes as far as any particular bank contact is concerned it being so arranged that depending on the particular wiper in contact with a bank contact, one or other of the brushes is efiective to complete a connection over the switch. a

In one form of construction the several wipers of a set may be formed out of the same piece of metal and may be of the nature of a multi-armed spider mounted on a spindle. Secured rigidly to the spindle may be a collector ring having its circumference divided into two segments, one being of metal and connected electrically to the spider, the other being of insulating material or of metal insulated from the remainder of the assembly. A number of brushes equal to the number of 45 arms of the spider and spaced equally with them may be arranged to make contact with the collector ring the metal segment of which connects the spider to one of the brushes, the r brush conne ted depending on the particular arm of the spider that is in the bank, the other electrically and, by means of suitable brushes brushes at that time resting on the insulated segment of the ring.

In another form of construction the several arms may be independent and insulated from one another and from the spindle. For the purpose of connecting with the arms, independent brushes are provided each bearing on a collector ring, there being a brush and a collector ring for each arm of the switch.

Instead of the arms being equal in number to the brushes they may be a multiple of the latter.

The collector rings may be in the form of a commutator or slip rings mounted on the spindle or they may take the form of concentric strips in the bank, the wipers being arranged to bridge a metal strip and a bank contact the several wipers contacting with different metal strips.

In another form of construction the wipers of a set are electrically connected to a metallic hub secured to the switch spindle and rotatable with it; In close contact with the hub is mounted an insulating washer and depending on the side'of the hub on which the washer is mounted either the hub or the washer is cut away in parts to allow one of the brushes to contact with the hub for any position of the wipers with regard to the bank contacts, the whole forming a commutator device.

In the case when the washer is cut away the hub may have depressions formed in it, the parts depressed entering the cut away parts of the washer so as to provide a substantially flush surface for the brushes the whole presenting the appearance of a commutator with a fiat contacting surface.

In the preferred form the depressions are spaced equally around a circle concentric with the spindle on which the device is mounted. The projections formed on the under side ofthe hub project through cor responding apertures in the Washer so that they come into contact in succession with the brushes as the spindle is rotated.

The commutating device described allows all the brushes to enter the switch at substantially the same point and the brushes may conveniently be held in the same mounting as the bank contacts, but in a different plane to the bank contacts to avoia contact with the wipers during their rotation.

In the application of the invention to a telephone system a number of arrangements may be employed.

In one example the following arrangements may be employed. A number of backward hunting switches (call finders) operate on a multiple and by means of their several sets of brushes have access to links connected to the multiples of different panels which may be served by similar switches or therwise. lVhen a call arrives in the multiple of the call finders, a switch which receives the next dialled digit determines to which panel or group of panels the call is to be extended and hunts for and starts a call finder having access to the particular panel or group of panels, the switch started being one which, over one of its wiper sets, is able to extend the call to a free link in the desired panel or group of panels.

In another arrangement call finders and forward hunting switches are connected back to back, the call finders being switches embodying the invention. The several links from a call finder may give access to different panels of forward hunting switches and when a call finder is started it rotates until it is able to connect the calling line to a forward hunting switch in a panel which has free outlets available for the extension of the connection. If a call finder is prevented from extending a connection owing to there Y being no available outlets, arrangements may be provided to prevent such a call finder being taken into use.

Any of the well known methods of allocating call finders for use may be employed.

In another arrangement the inverse of the above may be employed, the call finders being of the ordinary type and their wipers connectable to for ard hunting switches in different panels, the forward hunting switches being switches embodying the invention.

Reference will now be had to the accompanying drawings which show by way of example embodiments of the invention.

Figs. 1 to 6 show diagrammatically portions of rotary stepping switches each having three wipers set at an angle of 120 to one another and mounted on a spindle and co-acting with the same bank contacts. Three different brushes or feeders are used, one for each of the wipers, and a bank contact may be put into connection with one of three circuits by means of the brushes and depending on the wiper engaging the bank contact. It is of course to be understood that the switch will have other wipers and bank contacts which would be similarly arranged, for completion of circuits for conversation, testing and so on, the wipers in the circuit of one wire only being shown for the sake of clearness. Figs. 7 to 10 show circuit arrangements in diagrammatic form employing switches embodying the invention.

Referring to Figs. 1 and 2, these show an arrangement in which three separate wipers, 1, 2 and 3 insulated from one another and from the spindle on which they are mounted lie in the same plane and co-act with the same set of bank contacts 4. The wipers are mounted on a spindle which passes through the central hole 5 and on the spindle and adjacent to the wipers are three sliprings 6, 7 and 8 insulated from one another and from the spindle and on which bear brushes 9, 10 and 11 connected to a further circuit. Each of the wipers is connected to one of the sliprings so that, depending on the wiper engaging a bank contact the connection is extended over one of the brushes 9, 10 or 11 to one of three circuits. The wiper spindle may be rotated by any convenient means such as by a pawl and ratchet mechanism, the ratchet being secured to the spindle and designated 12 on the drawings. The brushes 9, 10 and 11 may all bear on the sliprings along a line parallel with the wiper spindle and may all enter the switch from the same direction.

In Figs. 3 and 4 the three wipers are stamped from a single piece of metal and are mounted on the spindle adjacent to a commutator 6. This commutator is in the form of an insulating ring or cylinder having a metal segment 7 inserted at a portion of its surface, the exterior of the segment being flush with the surface of the insulating ring, the segment extending over one third of the circumference of the ring or cylinder and being electrically connected to the wiper stamping. Three brushes 9, 10 and 11 bear on the surface of the commutator at points spaced 120 apart and the commutator is so mounted with respect to wipers that as one wiper for example the wiper 1 enters the bank, assuming a clockwise rotation, brush 9 comes into contact with the metal segment 7 and if the switch is brought to rest with wiper 1 in engagement with a bank contact, the circuit is extended over brush 9. When, by continued rotation of the wiper spindle wiper 1 steps out of the bank brush 9 leaves the segment 7 and as wiper 2 enters the bank the wiper stamping is connected by means of the segment 7 to brush 11 over which the connection will be extended if the switch is brought to rest with wiper 2 in the bank. The spindle may be rotated by a pawl or ratchet mechanism, the ratchet being secured to the spindle and designated 12 in the drawings.

Figs. 5 and 6 show a further modification which permits the use of a single wiper stamping yet allows the brushes or feeders to enter the switch substantially at one point. The bank contacts 4 are assembled in arcusulated therefrom and from one another. 10 contacts are shown 1n the present example.

5 At one end of the bank and in a difierent plane from the bank contacts are mounted three feeders or brushes 9, '10, 11', these beingclamped between the mounting'plates in the same manner as the bank contacts. The tips of the feeders are bent up towards the wiper stamping as may beseen in Fig. 6.

Three wipers 1, 2, 3, spaced 120 apart are stamped from a single piece of metal and take the usual shape as will be seen in Fig. 5, but with an enlarged hub. The wiper stamping is mounted on andinsulatedfrom a spin dle 5and in the radial width of the hub the metal is punched to form projection 7 on the underside of the stamping spaced around a circle concentric with the spindle 5. Assembled on the spindle 5 and beneath and in close contact with the wiper stamping is a thin insulating washer 6 which is cut away in parts to permit the raised parts on the underside of the wiper stamping to project through the washer. The tips of the brushes 9, 10 and 11' normally rest on the washer 6 and are so situated as to make contact one at a time with the projections 7 as the switch spindle is rotated the spacing between adjacent projections being greater than the width occupied by the three brush tips. The brushes are of springy material so that a good contact is made when a brush engages a projection. As the wiper spindle is rotated the projections come into contact successively with the three brushes so that a wiper tip is put into contact with each of the three brushes in turn as it is stepped round the bank. It will be seen that a wiper tip on passing over the bank connects every third bank contact to the same brush and it Bank contact Projec- Brush No. on

Bank contact Projection N 0.

L tea is to leave the wiper stamping flat d form the ti s of the brushes so that a 1. makes contact with the wiper stamping 'ough holes in the insulating washer which wou d be very thin in order that the brush movement would be slight.

in a further alternative construction the ins lat-lug washer may be placed on the side of bill, stamping remote from the brushes, the .stan ping being cut away in parts so that normally the brush projects through the stamping and clear of it and rests on the insulating washer. l fith these forms of construction the brushes may be spaced 120 apart and slot extending over 120 or 240 as the case in ay be'would be cut in the washer or wiperstamping depending on the construction employed. This arrangement of brushes is however not very convenient and by using the form of construction shown in Figs. 5 and 6 the brushes may be situated close together.

Vl 'h'ere double'sided wipers are employed, i. e. the wiper tip engages both sides of a bank contact care must be taken that the brushes do not pass throughthe two parts.

of a wiper so that the a i er tips contact with the brushes in certain positions and connect two brushes together. In order to avoid this, single sided wipers are preferred and by mounting the brushes in a different plane from the bank contacts this difliculty does not occur.

Reference will now be made to the circuit arrangements employing switches with three ssts of brushes per wiper set. Figs. and

l a show an arrangement 'in which the switches are call finders, Figs. 8 and 8a an arrangement in which the switches are nonnumerical forward hunting switches and Figs. 9, 9a, 10'and 10a show arrangements uitable for use with a by-path system.

7 call finder this is a switch having In Figs. 7 and 7e are shown an incoming line circuit LC, a call finder CF having wipers adapted to be connected to any one of three link circuits CC to a non-numerical forward hnn ing switch MS which for convenience will be referred to as a mixing switch. The line circuit is connected in multiple to bank contacts in a group of call finders, and each link circuit is multipled with similar circuits from other call finders to a mixing switch.

An assi ner AS for each group of lines is provided, its function being to search for and assign for use a free link circuit. The

individual line and cut off relays are designated L and K respectively and the common start relay in the assigner is designated S. AK is the assigner test relay, and DA the call finder test relay with an auxiliary relay DB.

The assi 'ner ste 3 )in ma 'net is desi nated DM, the call finder magnet DF M and the mixing switch magnet DSM. The line and test relays of the mixing switch are designated R, and T respectively. As regards the wipers each wiper comprising 3 contact making members spaced 120 apart and adapted to be put into contact with one of a set of 3 brushes p, q, r. The wipers and brushes of the call finders may be of any of the types ping the assigner. If the mixing switch connected to the contacts with w 1lCl1 the assigner is in contact is busy earth will be connected over the test wiper of switch MS or over contact 81 of another assigner to the contact in the bank of wiper N1 of the as signer and relay AK will be short circuited. If the mixing switch MS is free but the call finder CF is engaged over one of its other brush sets with another mixing switch such as the switch connected to the wires MSl relay AK will be short circuited by earth over contact cZaS of the call finder and wiper W2 and contacts 81. The magnet DM accordingly operates to one of these earths and steps the assigner until contacts connected to a free mixing switch associated with the call finder CF are encountered whereupon relay AK being no longer short circuited operates in series with magnet- DM and at contact 61/ 171 opens the magnet circuit and extends earth over contacts 81 and s2 and wiper W1 to the link circuit test wire to mark the mixing switch engaged to the assigners associated with other groups of lines. Magnet DM does not operate in series with relay AK. Contact (1702 opens to guard the magnet circuit against closure of contact 4M8 when the calling line is found by the call finder. Contact (1/03 prepares the circuit of relay X and contact (an prepares the call finder testing circuit. Contact ale-5 closes a self-driving circuit for the call finder magnet DEM. The call finder CF being assumed to be free magnet DF M operates and by interrupting its own circuit at contact dfm steps the wipers of the call finder round until the marked bank contact is put into connection with the middle brush 9. \Vhen this occurs a circuit is closed from earth over contact a704, wiper 4 centre brush and wiper CFS, winding (1) of relay DA, centre brush and wiper CF23, contact Z1, relay K to battery. Relay DA operates and at contact (la? opens the driving magnet circuit. Contact (Zal closes an energizing circuit for winding (11) of relay DA and contact (M3 closes a parallel circuit for energizing relay DB. Contact ch12 short circuits winding (I) of relay DA and relay K operates and at contact 701 closes a holding circuit for itself against the release of relay L which takes place when contacts 702 and 703 are open. Contacts (Z05 extend the call finder test wire through to the switch MS and the speaking and metering wires are similarly extended at contacts (Z04, (Z and (Z66. Contacts dat, (ZaG and the remaining contacts of relay DB perform similar functions should the call finder have been connected over one of its other brush sets to another mixing switch such as the switch MSl.

Consequent on the operation of relay DB relay R of switch MS is connected over contacts t2 and 253 to the calling subscribers loop and operates over this circuit and at contact 1 1 connects earth to the test wire to hold relays K, DA and DB after relay AK releases. At contact 72 a circuit is closed for magnet DSM over contact 251 wiper MS3 and normal contact, contacts 73 and 1 1 to earth and the switch wipers are stepped into the bank and search for a free first selector takes place. The driving circuit during search is over contacts r2, t1, wiper MS3 to the busy earth in the test wires, relay T being short circuited during stepping over busy contacts in the usual manner. When an outlet to a free selector is encountered relay T is no longer short circuited and there is no earth for the magnet DMS consequently the switch is brought to rest and relay T operates. Contact t1 opens the driving circuit and extends earth over contacts 11, t3 and wiper MS3 to busy the outlet. Contact 256 closes in parallel with contact 1 3 and relay R is disconnected at contacts 252 and t3. Contact it opens the opening the circuit of relay X at contacta7c3 and the circuit of the call'finder magnet at contact (i705.- Contact 05704 disconnects earth over w1per ll l from the link circuit test wire but earth is now connected thereto first overv contact r1 and later consequent on the seizure or" a free first selector by'earth applied to the incoming test wire by the selector release relay. On the closure of contact @702 the 'assigner is stepped on until contacts associated with a free call finder are encountered. Relay X is released at contact @763 and the assigner is now in a condition to effect ,a further assignment. To meter the call battery is connected to the metering wire at a. subsequent selector, the metering circuit being over wiper MSA, contacts t5, (Z56, centre brush and wiper CF 1, meter M to earth.

At the end of the conversation when the calling subscriber replaces his receiver the line relay at the first selector releases and is followed shortly after bythe release relay which disconnects earth from the test wire releasing relays T, DA, DE and K. Belay T releasing the homing circuit of the switch MS is closed at contact t t and the switch is rotated to normal. The call finder remains in the position in which it was last engaged.

A group control circuit may be arranged to connect earth over wire gp and contact 66 to the link circuit test wire when all the outlets from a mixing switch are busy th'us preventing a switch which is not able to extend a connection from being assigned.

Referring now to Figs. 8 and So these show a similar arrangement but the call finder is of the ordinary type and the mixing switch is of the type having wipers connectable to 3 different incoming circuits. The relay and magnet designations are the same as in Figs. 7 and 7a. he callfinder wipers are multipled over a number of mixing switches, the cal. finder CF shown in the figure being connected to the middle brush 7 of the brushes g), Q? r of the switch MS and to similar switches. The brushes 7) and r are connected to wires incoming from other call finders having access to the switch.

-Nhen a cal is made relays L and S operate and assigner is set in motion to search for a free mixing swi ch associated with a free call finder. Such a switch is denoted by the absence of earth in the corresponding contacts in the banks ofwipers W1 and W2 gages the link. It being assumed that the switch MS is the one assigned and that this switch is connected to the call finder CF over its centre set of brush-es q, the switch will be constrained to test in only when its wipers are connected to the centre brushes. If the wipers are in connection with one of the brush sets p or 1 there will be a circuit for magnet DSM over off-normal segment and wiper MS6, br'ush p orr wiper NVt or W5 and contact (1704i or to earth. The magnet operates in this circuit and by interrupting its owncircuit at contact (ism steps the'wipers untilthey are brought into connection with the 'centre'brush. When this connection is made the circuit over wiper MSG is open and stepping depends on the condition found in the bank contact of wiper MS? When a free outlet is found with the wipers connected to the centre brush relay'T operates; opens the magnet circuitat contact :61 and connects relay T to the test wiper MS3, theearth-for' relay T being over wiper NVl and contacts a701, s2 and 81. Contact t3 closes a circuit for the auxiliary relay TA and contacts of this relay and contact 22 connect the several brushes of the switch to the wires incoming from the call finders having access to it. Earth over wiper VVl is now connected over contact t2. segment and wiperMS5, centre brush, contacts dual and clfm to magnet DFM which operates and by interrupting its own circuit at contact dfm steps the call finder in search of the calling line. When this is found relays DArand K operate and thesubscribers loop is extended over contact dad and (M5 to the selector seized by the switch MS and contact da? closing relay X operates and disconnects the start relay S. Relay S releases followed by relay AK and the as signer is stepped to contacts connected to a free call finder denoted by absence of earth in the bank contact of wiper W2.

Metering takes place by the connection of battery at a selector circuit .to the wires outgoing from the contact in the bank of wiper MS l.

At the end of the conversation relays T, DA and K which are held by earth fed back from a subsequent selector release consequent on the disconnection of this earth and the switches remain in the. contacts they last engaged.

q The wires 9 and h outgoing from the assigner banks are connected to other mixing switches connected with the same call finder.

Figs. 9,9a, 10 and 10a show an embodiment of the invention ina by-path system. Figs. 9 and 9a show in schematicfo rm the eonnections of the switches of two switching stages while Figs. 10 and 10a show diagrammatically an arrangement for the switching stage shown in Fig. 9.

A link circuit LK can only be picked up from a previous switching stage when the associated by-path circuit BP common to a panel of switches in the switching stage now to be taken into use is free. When such a link circuit is picked up the associated bypath circuit is prepared to receive impulses and the next impulse train dialled is received in the by-path circuit which includes a two motion switch which responds to impulses and is stepped thereby to a level depending on the number of impulses in the train. It then rotates over the level in the usual manner in search of a free switch in the panel such as those denoted SC which has a free outlet to the required group of the next switching stage. The seized switch SC then searches for the link circuit LK and when this is found with the wipers connected to the appropriate brushes as determined by the setting of the by-path circuit switch the by-path circuit is released and the calling line is extended to the next switching stage.

In Figs. 9 and 9a the outlets from the bypath circuit switch to the switches SC in the panel are denoted by j while the outlets from the switches SC in a forward direction are denoted by 70. These outlets 7c of the panels of switches in the particular switching stage are connected to one side of a distributing frame and outlets of panels in the same group may be commoned and indicated by the dotted lines cross connections being made as desired to the other side of the frame which is connected to panels in the groups of switches of the next switching stage. The switches SCI in ten groups of this latter stage are shown diagrammatically in Fig. 9a only one panel in each group being indicated, the wires m on the left of these switches representing inlets to panels of switches in a group. Between the incoming wires m from the distributing frame and the switches SCl are connected link circuits LKl common to a panel of switches the link circuit for a panel having an associated by-path circuit ar ranged in a. similar manner to that shown on the left of the drawing.

The circuit arrangements for one link circuit and a panel of switches with the associated by-path circuit are shown in more detail in Figs. 10 and 10a.

Referring now to these figures the link circuit is designated LK, the by-path circuit BP and the by-path switch BPS. The switching circuit comprises the switch SC which is of the call finder type and has access to 3 outgoing circuits over 3 sets of brushes one of which is selected in accordance with the dialled digit received by the switch BPS.

The link circuit LK is accessible to switches of a preceding switching stage and can only be picked up when the associated by-path circuit is free. The circuit for testing for a free link circuit is over wire 0 contact M2 of test rela KL in the link circuit, relay T contact t1, the wire common to all the link circuits of a panel of switches, contacts 131,7t3 resistance to battery. Vlhen the switch in the preceding switching stage in the course of its ch encounters battery potential on the test wire it tests in and connects earth to the test wire to mark the link engaged. Relay T operates and at the front contact of its makebefore-break set #1 closes a circuit for relay X in series with itself. Contact 001 opens to engage the by-path circuit against other inlets to the panel. The wires Z) and c are extended to the by-path circuit over contacts 153 and t2 and relay A operates over the former circuit from battery connected at the preceding switch. On the operation of relay A contact a1 opens to guard the vertical magnet VM of the switch BPS and contact (12 closes a circuit from eartl over wire 0, contacts 252 and 111 for the dialling relay D which is of the slow to release type. Relay D operates and prepares at contact (Z1 a holding circuit for itself during impulsing, and at (Z2 a circuit for the vertical magnet. lVhen the first impulse of the next train arrives, relay A releases and the vertical magnet is operated. The circuit for its operation is from earth over contact M2 of the by-path switch test relay, contacts (Z2, a1, magnet VM to battery.

he magnet raises the Wipers opposite the first level and the vertical off-normal con tacts n1, 722 and R3 are operated. Contact n1 closes on the holding circuit of relay D and by opening its back contact prevents that relay being again energized by any further impulse trains that might be received by the switch, contact 112 closes a point in the circuits of the rotary and release magnets and contact a3 opens a further point in the test in circuit over the link circuit. Subsequent impulses of train step the switch wipers vertically to the required level and at the end of the train relay A remaining operated relay D releases and at contact (Z2 closes a circuit from earth over contacts ad2,d2,n2,a3,rotary magnet RM, interrupter to battery. The rotary magnet operates by means of the interrupter and steps the wipers round the level in. search of a free outlet from a free switch such as SC in the panel associated with the link circuit LK. Such an outlet is denoted by battery potential on the bank contact of wiper W4- and when the wipers are stepped to such a free outlet relay TD operates in a circuit from earth on wire 0, contacts 69, a2, winding (1) of relay TD, wiper 3V4 and one of the contacts 704-, k5, M5 in the switching circuit according to the line over which the test is made to battery. For the sake of ample it will be assumed that the circuit conn cted to the centre brush 9 of the three brushes 2 r, of the switch SC is selected,

iii)

the selection being in accordance with the digit which eilected vertical stepping of switch BPS. Relay TD operating contact tall closes a holding circuit over its winding (II) anc contact M3 connects earth directly to wiper We to mark the outlet engaged. Contact 6552 opens the rotary magnet circuit, contact t- Z connects the incoming 6 wire through over wiper W2 to the seized outlet, and disconnects relay A, contact 'td5 connects earth to wiper N1 to operate the stepping magnet DM of switch SC and M6 connects earth to wiper W3 to constrain the switch SC to test in with its wipers in contact with the centre brush. Magnet DM op crates in the above traced circuit and by means of the interrupter steps the wipers round the bank until the marked outlet is encountered by wipers connected to the centre brush. lVhen this occurs relay TF operates in a circuit from earth over contact tale, Wiper V3 centre brush and wiper SC l, winding I of rela TF centre brush and wiper 8C3,

contact 254 relay KL to battery. Contact tfl connects winding (II) of relay TF in parallel with relay KL and contact #2 short circuits winding (I) of the test relay of the switch SC. This relay now holds by means of its second winding and relay KL operates. Contact til closes a circuit for the auxiliary switching relay K which operates and the circuit over wipers of switch SC is extended .over contacts 702, 2?;6 and 705 to the outlet from the panel. Contacts/ 01, k3, 704:, I06 and 5 5, if? extend the wipers to other outlets when either of the other brush sets are in use. The stepping magnet circuit is opened at contact #3. Relay KL operating contact kll closes inparallel with contact tl and contact M2 changing over relays T and X are released and earth on wire 0 is extended to hold the relays I L and TF. Contacts t2 and 1 3 opening relay TD releases and the circuit of release magnet ZM is completed from earth over contacts M2, (32, n2, a3, magnet ZM to battery and the switcn BPS is restored to normal. Contact 118 being restored the by-path circuit is rendered accessible to another inlet to the panel.

The connection is then extended over the next switching stage in a similar manner and finally to the called line.

At the end of the conversation earth is removed from the test wire and relays KL, TF and K release and the switching and link circuits are ready for further use.

After the setting of switch BPS should a further train of impulses be dialled before the link circuit L K has been found by the switch SC the impulses will be repeated over wire F2, cent.- as 6e 4, wiper i i 2 outlet from the panel to the succeeding link and by-path circuits.

I claim:

1. In a rotary switchmechanism in which l and 396 a set of fixed contacts are successively engaged by a plurality of movable contacts and wherein the movable contacts are electrically connected, the provision of a like plurality of brushes and a cooperating commutating device comprising an insulating ring with a metal segment which functions to sequentially electrically connect said brushes with said movable contacts as the movable con tacts successively engage the contacts of said fixed set.

2. In an electromagnetic switch, a bank olf sets of contacts, a plurality of wiper sets, means for successively moving said wiper sets over said sets of bank contacts a plurality of brush sets for said wiper sets, and means comprising a ring member operated with said wiper sets to successively electrically connect said brush sets with the wiper sets as they successively pass over said sets of bank contacts.

3. In an electromagnetic switch a bank of sets or" contacts, a plurality of wiper sets,

means for moving said wiper sets over said.

bank contact sets in sequence, a plurality of collecting brush sets included in said bank contact sets, and means including projections on said wiper sets for electrically associating a different one of said brush sets with said wiper sets each time one set of said wiper sets passes oft a set of bank contacts.

In a telephone system, calling lines. call finder switch having access to said lines, a plurality of link circuits individual. to said finder switch extending from said call finder switch in the direction of called lines, and each link terminating in ahunting switch having access to trunks also extending in the direction of called lines, means operated consequent to the initiation of a call by one of said lines to select one of said link circuits, means operated consequent to the selection of a link circuit to cause said call finder switch to operate and connect the calling line to the selected link circuit, and means for then causing the hunting switch of such link to further extend the connection over an idle trunk.

5. In a telephone system, calling lines, call finder switches having access to said lines, a plurality of link circuits there being but one extending to each of said call finder switches, a trunk hunting switch in which all of said link circuits terminate, means operated consequent to the initiation of a call by one of said lines to select one or said link circuits, means operated consequent to uch selection to cause the associated trunk hunting switch to connect such link with an idle trunk, and means for then operating the call finder to also con nect the link with the calling line. 7

6. In a telephone system, group of lines, a group of trunk lines, a group of trunk hunting switches having access to said trunk lines, a call finder switch having access to said lines, a group of link circuits extending from said call finder switch and each terminating in one of said hunting switches, means for making said link circuits busy, a link circuit assignor switch operated consequent to the initiation of a call by one of said lines to assign an idle one of said link circuits for use by the calling line, an operating circuit for said call finder also completed by said assignor switch, and means also operated consequent to the initiation of the call to cause said finder to stop when the calling line is connected with.

7. in a telephone system, calling lines, call finder switches each having a plurality of paths over which they may seize and connect with said lines, trunl: hunting switches individual to the respective paths of said finder switches, means responsive to the initiation of a call by one of said lines for selecting an idle one of said finder switches and an idle one of said paths, and means responsive to said seizure for operating said finder switch to seize and connect the calling line over the selected path to the hunting switch individual to such path.

8. In a telephone system, a calling line, a call finder having a plurality of paths over which it may seize and connect with said line, a trunk hunting switch individual to each of said paths, and means responsive to the ini tiation of a call on said line for operating said finder to find and connect the calling line over one of said paths to the hunting switch individual to such path to extend the connection in the direction of 21 called line.

9. In a telephone system, a first group of lines, a first finder for finding calling lines in said first group, a seconc group of lines, a second finder for finding calling lines in said second group, atrunk hunting switch normally connected to both said first and second finders, means responsive to call in the first group foroperatingsaid trunkhunting switch to find an idle trunk and the first finder to find the calling line to extend the call in the direction of a called line, and means responsive to av call in the second group for operating said trunk hunting switch, if idle, to find an idle trunk and the second finder to find the calling line in the second group to extend such call in the direction of the called line.

10. In telephone system, a plurality of lines, a plurality of finders having access to said lines, a plurality of trunk hunting switches, a plurality sets of conductors terminating in each switch and each set of conductors terminating in a differentone of said finders, and means responsive to a call by one of said lines for selecting an idle one of said switches and the set of conductors in said switch which terminates in the finder having access to the calling; line.

11. In a telephone system, a plurality of lines, a plurality of finders having access to said lines, a plurality of trunk hunting switches, a plurality of sets of conductors terminating in each switch and each set of conductors terminating in a different one of said finders, and means responsive to the initiation of a call by one of said lines for operating the finder having access to said calling line to connect the calling line to a particular one of said hunting switches by way of the set of conductors terminating in both the said finder and said switch.

12. in a telephone system, a plurality of lines, a plurality of finders having access to said lines, a plurality of trunk hunting switches, a plurality of sets of conductors terminating in each switch and each set of conductors terminating in a different one of said finders, means responsive to the initiation of a call by one of said lines for selecting an idle one of said hunting switches, means responsive to said selection for operating said selected switch to find an idle trunk and complete a connection between said switch and the particular finder havin ccess to the calling line over the set of conductors terminating in such finder, and means responsive to said last means for operating said finder to find the calling line and connect such line to the selected idle trunk by way of said set of conductors.

13. In a telephone system, a plurality of groups of lines, a finder individual to each group of lines and each finder having access to the lines in its individual group, a trunk hunting switch common to said groups of lines for selecting an idle trunk, a plurality of sets of conductors terminating in said switch and each set of conductors terminating in a different one of said finders. means responsive to the initiation of a call by a line in any one of said groups for selecting said switch if idle, means responsive to said selection for operating said switch to connect an idle trunk with the particular one of said sets of conductors terminating in the particular finder having access to the said calling line, and means for operating said particular finder to connect the said calling line to said idle trunk by way of said particular set of conductors and said switch.

14. In a telephone system, a plurality 01 groups of lines, a finder individual to each group of lines and each finder having access to the lines in its individual group, a trunk hunting switch common to said groups of lines for selecting an idle trunk. a plurality of sets of conductors terminating in said switch and each set of conductors terminating in a different one of said finders. means responsive to the initiation of a call by a line in any one of said groups for selecting said switch if idle, means responsive to said selection for operating said switch to connect an idle trunk with the particular one of said sets of conductors terminating in the particular finder having acce s to the said calling line, means for operating said particular finder to connect the said calling line to said idle trunk by Way of said particular set of conductors and said switch, means dependent upon the group the calling line is located in for determining the particularset of conductors to be used in extending the i call, and means for thereafter operating said switch and the finder associated with said determined particular set of conductors to connect an idle trunk with the calling line over said set of conductors.

15. In a telephone system, lines, a finder having access to said lines, a plurality of trunk hunting switches for selecting idle trunks, a plurality of sets of conductors terminating in said finder and each set of conductors being individual to a different 7 trunk hunting switch, means responsive to the initiation of a call by a calling one of said lines for selecting any idle one of said switches, means responsive to said selection for preparing a test circuit including the set of conductors individual to the selected switch, means for thereafter operating said finder in search of the calling line, and means operative responsive to said finder connecting the calling line with said prepared test circuit for stopping said finder and for connecting the calling line to said selected switch by way of its individual set of conductors.

16. In a telephone system, lines, a switching mechanism, a bank of contacts in said mechanism terminating said lines, wipers in said mechanism for engaging said contacts, a plurality of circuit paths in said mechanism, means responsive to the initiation of a call by a calling one of said lines for preparing one of said circuit paths and for operating the wipers of said switch mechanism, means responsive to said operation for successively establishing said circuit paths through said wipers to said contacts, and means for stopping said wipers in response to any one of said Wipers connecting the bank contact of the calling line to the said prepared circuit path.

In testimony whereof I affix my signature.

DAVID ADAM CHRISTIAN.

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