US2176340A - Telephone system - Google Patents

Description

31?, @3%. E. A. HENsLR ET Aa.

TELEPHONE SYSTEM 7 Sheets-Sheet l Filed March ll, 1937 l i o. 00

E. A. HENSLER Er A1.

TELEPHONE vSYSTEM 7 Sheets-Sheet 2 Filed Hal-ch ll. v1937 FCZ Get. T @39 e. A. HENSLER 'Er AL TELEPHONE SYSTEM Filed March 2.1, '7 Sheets-Shes?. 4

Oct. 17, 1939. B. A. HENsLl-:R ET A1. 2,176,340

TELEPHONE SYSTEM Filed March l1, 1937 7 Sheets-Sheet 5 729772.69 Za. aff, @awa/jules @y CMW M' Oct. 17, 1939.

B. A. HENsLl-:R Er AL. 2,176,340

TELEPHONE SYSTEM Filed March 11,' 1957 7 sheets-sheet s l w, HG 6 r? ju 0B /IJ @R k7 6 T RA 604 *Z* CAI-:I

' STW U lli-- J NSK Oct. 17, 1939. B. A. HENsLr-:R Er Al. 176340 TELEPHONE A SYS TEM Filed March 11,'19'57 7 Sheets-Sheet 7 Patented Oct. 17, 1939 UNITED STATES PATENT OFFICE Humphries, London,

England, assignors to Siemens Brothers c Company Limited, London, England Application March 11,

1937, Serial No. 130,389

In Great Britain March 16, 1936 Claims.

This invention relates to telephone systems and is concerned more particularly with improvements in call distributor arrangements wherein provision is made for forming calls into .s a queue as they arrive so that they may be dealt with in the order of their arrival. It has already been suggested to arrange that the queue is formed by distributor switches associated with incoming lines and operating in conjunction 10. with a lamp display circuit. In one form of this arrangement as disclosed in the application of Hensler and Peters, Serial No. 37,484, filed August 23, 1935, means are provided in the lamp display circuit for bringing about the sending u. of` a control signal to one or more omnibus operaQTs positions when the number oi calls waiting in the queue `reaches a certain gure or when the condition arises that a call has been waiting in the queue for a time suflicient to alo low the two relays of a time-measuring device to be operated in sequence by timed pulses. The time which elapses between the joining of the queue by a call and the sending of the control signal due to the occurrence of the condition ,just mentioned is not very precisely determined as it depends upon the part of the time pulse cycle at which the relevant relays happen to be connected to the pulse wires. Separate timemeasuring devices are provided for each call 3a waiting in the queue.

` The present invention relates to modied circuit arrangements for a call distributing system wherein a lamp display circuit is employed, and has especially in view the provision in the lamp am display circuit of improved means for determining that a call has been waiting for a predetermined time and for bringing about an indicating action such as the sending of a control signal as just described when the condition arises that Ya call has been waiting for this time. The arrangements according to the invention make it possible readily to arrange that the said means is such that a substantial portion of the apparatus concerned is common to all the calls wait- 45; ing in the queue and that the period for which a call has been waiting is determined more precisely than in the arrangements described in the above-mentioned application.

According to the invention, in a telephone 50, system provided with call distributing arrangements for connecting calls to subsequent circuits and so arranged that if free subsequent circuits are not available each call causes the setting of switching apparatus to a position indicative of 55 its order of arrival with respect to other calls thereby forming a queue, arrangements for indicating that a call has been waiting in the queue for a predetermined time are such that a call on entering or starting a queue has directly associated with it a device the condition of which changes continually while the call is in the queue so that the attainment of a particular condition serves to indicate that the predetermined interval has elapsed.

In an arrangement contemplated, the lapse of a predetermined time as regards a call is signied by the attainment by a condenser of a certain state of charge, the said condenser being connected to a charging circuit when the relevant call assumed the waiting condition. Normally, of course, the charging circuit would include a high resistance in order to make the charging time sufficiently long. The action such as the send-ing of a control signal is brought about when the said state of charge is attained by means of a thermionic valve which at the time concerned has a control grid connected so that its potential depends upon the potential difference between the terminals of the condenser andthe anode current of which controls one or more relays. The number of condensers provided corresponds to the maximum number of calls which can be accommodated in the queue, there being switching arrangements adapted to connect the several condensers individually to the circuit of the control grid as circumstances require. It should be noted that the arrangement is such that the predetermined time may readily be varied to suit varying circumstances by altering the sensitivity of the anode circuit 35.

relay or relays and/or by altering the value of the resistance of the circuit in which a condenser is charged.

The features of the invention are exemplified in the call distributing arrangements embodying 40 it which will now be described with reference to the accompanying drawings.

Figs. 1-5 of the drawings show an incoming line circuit, a call distributor circuit, and a lamp display circuit arranged for use in association with one another. Figs. 6 and 7 show an alternative form of line circuit arranged for use in direct association with the lamp display circuit without separate intermediate call distributor circuits. This alternative form of line circuit provides for bothway working over the line concerned. The circuits shown in Figs. 1-5 resemble in many respects the corresponding circuits illustrated and described in the prior application. In particular, the arrangements for the is a control wiper.

formation of a queue shown in Figs, 2-5 are broadly similar to the corresponding arrangements of the said prior application.

Referring firstly to the incoming line circuit shown in Fig. 1, this includes a single-motion line switch the outlets of which give access to call distributor circuits such as that shown in Figs. 2 and 3. The line switch has a stepping magnet DM and wipers PI, P2, P5. Wiper PI The switch is stepped by interaction between magnet DM and contact dm thereof. The incoming line is connected to the positive and negative wires shown incoming on the left of the iigure. When the line assumes the calling condition, line relay L is operated over the calling loop in the usual manner. Contact ll connects earth to the private or P wire, contact Z2 prepares the circuit of high-speed test relay T, contact Z3 prepares the circuit of wiper switching relay H, contact Z4 prepares la circuit which only comes into operation if the line switch encounters congestion, and contact Z5 completes a self-stepping circuit for the line switch so that the wipers are stepped from the normal position. After the Wipers have left the normal position the self-stepping circuit passes over wiper Pi and back contacts h4 and tl.

If and when a free outlet is encountered, test relay T operates on its windings (I) and (IT) in Series with a dry-plate rectifier, the private or P wires of free outlets being connected to battery over resistances such as YC in Fig. 2. The single change-over contact tl of relay T thereupon opens the short-circuit about the winding of relay H which exists over contacts tl, h4, and Z3 during the stepping of the switch so that the latter relay is inserted in series with stepping magnet DM. The magnet will not operate in series with relay H but relay H operates. The switch wipers are thus brought to rest on the free outlet, which is marked busy during the operation of relay H by being connected to earth via the low-resistance winding (II) of relay T and front contact tl. The rectifier serves to prevent false operation of relay T due to the presence on a test wire of a booster battery metering condition. When relay H operates, contact hl forms a through P wire and short-circuits relay T, contacts h2 and h3 extend the positive and negative wires of the line to the corresponding incoming wires of the seized call distributor circuit and release relay L, contact h4 closes an alternative circuit for relay H, and contact h5 connects earth to Wiper P5. As will be explained later in connection with Fig. 2, the connection of earth to wiper P5 only has an effect in the case where the incoming line is a call oice line. Relay H is held for the duration of the call by earth on the P wire, this earth being applied subsequent to the opening of contact l! at a point ahead of the line circuit. When relay H is released by the removal of this holding earth, contact hli closes a self-driving circuit for the line switch so that the wipers are stepped to the normal position. The self-driving circuit includes wiper Pi and back contact tl and, as regards the last step only, back contact Z4..

If no free outlet is encountered when the line switch makes a search, the wipers are driven to the last contact position from which they are stepped off by an earth pulse which is intermittently applied to the last contact in the bank of wiper Pl over a circuit including contact Z4 and pulse wire PW. The pulse may be given every three seconds. The line switch is thus caused to search at intervals until a free outlet is found. i i

Referring now to the call distributor circuit shown in Figs. 2 and 3, this is arranged so that, when the circuit is taken into use by an incoming line circuit and the motor-driven uniselector which forms the distributor switch is caused to test its outlets in search of one marked as selectable, the first outlet tested is an overflow outlet associated with the lamp display circuit, this being followed in turn by the queue-forming outlets to the lamp display circuit, a control outlet, and outlets to connecting circuits at operators positions. The four wires incoming from the multiple of the line switches of the associated line circuits are shown on the left of Fig. 2. Wire CO is only connected to .the relevant contact in the bank of wiper P5 in the case of those line switches which are associated with call office lines. The distributor circuit tests free to a searching line switch by virtue of battery connected to the incoming P wire over resistance YC and contacts 0112 and s6.

The motor-driven uniselector which forms the distributor switch operates at a high speed and has wipers 1 8. The uniselector is of the type in which the driving motor comprises two fixed electromagnets which operate on a magnetic rotary armature and are adapted to be alternately energised by contacts controlled by the movement of the armature and in which the movement of the wipers is under the control of a latch magnet. When the latch magnet of the uniselector is energised, a latch is Withdrawn from a toothed wheel forming part of the drivlng mechanism of the switch and thev circuit Vof the driving electromotor is closed at a contact of the latchk magnet, and in consequence .the wipers are rotated at a high speed. When the latch magnet is de-energised, the motor circuit is opened and the latching member engages the toothed wheel referred to, bringing the switch substantially instantaneously to rest. In Fig. 3 only the circuit of the latch magnet is shown, the associated motor circuit being omitted in order to simplify the diagram. The latch magnet is designated LM. The relay in series with it and designated RA is a magnet alarm relay. All the eight wipers of the uniselector are doubleended wipers of the type in which the two ends co-operate with different arcs of bank contacts. in the drawings the two arcs of contacts are indicated diagrammatically by full and broken lines. The wipers rotate in a counter-clockwise direction, the arc of bank contacts represented by a full line being traversed before that represented by a broken line. Contacts onl and 011.2 of the uniselector are off-normal contacts which are operated when the switch leaves its normal position and remain operated as long as the switch is away from this position. The wipers of the uniselector are divided into two sets, the set connected in circuit at any moment depending on the condition of a wiper choosing relay WS.

When the circuit is taken into use, line relay L is operated over the calling loop in the usual manner. Contact ll operates relay B in a circuit over back contact ssl. Contact bi connects a holding and busying earth to the incoming P wire, contact b4 closes a point in the circuit of high-speed test relay T, contact b5 closes a point in the circuit of latch magnet LM, and contact b connects the lower right-hand winding of four-winding line transformer or repeating coil TR to a source of ringing signal tone,

the circuit in which tone current is thus caused to ow being: source connected to Wire RS, wire RS, condenser QC, contacts h6 and S85, the said winding of transformer TR, earth. Transformer action causes a ringing signal to be Vreverted over the calling loop.

As soon as contact b4 closes, a test is made of the condition of the outlet on which the wipers of the uniselector normally rest. This outlet is an overflow outlet associated with the lamp display circuit and the test relay T is only operated with the wipers on this outlet when all the queue-forming outlets to the lamp display circuit are engaged. When relay T is so operated, its operating circuit is earth, bank contact and Wiper 5, contacts w85, S84, ds2, and b4, dry-plate rectifier, windings (I) and (II) of the relay, contact w56, wiper 'l and bank contact, resistance YG, battery via an overflow meter connected at the time to wire Cl in the lamp display circuit (Fig. 4) In these circumstances, the changing over of contact tl inserts the winding of relay S in series with latch magnet LM so that the relay is operated and the latch magnet is prevented from operating by the resistance of the relay winding, but the operation of the relay is without material effect. The operating circuit for relay S is battery, alarm relay RA, latch magnet LM, contacts b5, Zc2, and sl, Winding of relay S, earth. When the relay operates contact sl closes an alternative circuit for the relay over resistance YF and de-energises the latch magnet, contacts s2 and s4 apply earth to both sides of relay SS, and the remaining contacts have no effeet. The test relay T and auxiliary relay S are released andthe wipers of the uniselector set in motion as soon as a position in the queue becomes vacant. Relay T is released by the opening of the circuit of its holding winding (II) at contact of I in the lamp display circuit (Fig. 4), relay S is released owing to the fact that it is short-circuited by back contact tl, and the wipers are set in motion by the closure of a circuit for latch magnet LM over back contacts tl and sl. The latch magnet is operated in the same circuit in the case where relay T does not operate When'contact b4 first closes.

The circuit in which relay T is operated to bring the wipers to rest on a queue-forming outlet is earth, contact tot, bank Contact and wiper 5, contacts w55, sell, dsZ and b4, rectilier, windings (I) and (II) of the relay, contact w36, Wiper 1 and bank contact, battery connected at the time (Via certain apparatus) to one of the wires Tl-T4 in the lamp display circuit (Fig. 4). When relay T is so operated, the changingover of contact ti inserts the winding of relay S in series with the latch magnet and short-circuits the high resistance winding (I) oi relay T and the associated rectiel', thereby marking the outlet engaged and bringing about the operation of the test-wire relay in the display circuit. Relay S operates and at contact s3 closes an operating circuit for relay TC, this circuit being earth, contacts S83, s3, and wsli, wiper 3 and bank contact, winding (I) of the rela-y, battery. A short-circuit over Contact s2 and wiper I again prevents the operation of relay SS. Relay TC locks up in a circuit over contacts tcl, ds3, and Z3. Contact tot opens the testing circuits of the queue-forming outlets to the lamp display circuit, and contact fc prepares a circuit for stopping the wipers on the control outlet previously referred to.

When subsequent to this relays T and S are released due to the earthing of the relevant test Wire in the display circuit (which earthing signiies that the call is at the head of the queue and that there is a free assigned connecting circuit), the wipers are again set in motion but are stopped by the operation of relay T as soon as the control outlet is reached. The circuit in which relay T is operated in this case is earth, bank contact and wiper 5, contacts w85, ssd, ds2, and b4, rectifier, windings (I) and (II) of the relay, contact w85, wiper 'l and bank contact, contact tcE, winding (I) of relay DS and non-inductive shunt, battery. The changing over of contact tl rings about the operation of relay S as usual and also operates relay DS. Relay DS locks up on its Winding (Il) in a circuit over contacts dsl, 103, b2, and ssl, and at contact dsZ renders the uniselector testing circuit independent of wipers 5 and 6 and at contact d`s3 releases relay TC". A short-circuit over Contact s2 an-d wiper l again prevents the operation of relay SS. The opening of contact fc5 brings about the release of test relay T and its auxiliary S, and further rotation of the wipers ensues until either the outlet to a free assigned connecting circuit in the banks of wipers l, 3, 5 and 'l is reached or until the last position prior to normal is reached. It should be noted that the bank contacts engaged by the wipers of the uniselector in this position are not used for outlets to connecting circuits. If the said last position is reached during such a search the wipers are stopped by the operation of relay T in the circuit: earth, contacts dsZ and b4, rectifier, windings (I) and (II) of the relay, contact w35, wiper 1 and back contact, win-ding (I) of wiper choosing relay NS and non-inductive shunt, battery. Relay WS is operated when the contact tl changes over, and locks up on its winding (II), connects up the alternative set of Wipers of the uniselector, and prepares a holding circuit for relay LC. Contact ws! makes before the back contactsy of the relay open. The changing over of contact wsis releases relay T and further rotation of the wiper ensues, the outlets tested during such further rotation being those connected to the bank contacts associated with the alternative wiper set. The wipers pass through normal at a speed which is sufficiently high to prevent relay WS from being released by the momentary closure of contact oni?. In either of the two cases just mentioned, when the outlet to a free assigned connecting circuit is tested the Wipers are stopped by the operation o-f relay T in the circuit earth, contacts cls? and b4., rectifier, windings (I) and (II) of the relay, contact w66, wiper I or 8 and bank contacts, battery connected to the P wire of the connecting circuit. The rectier serves to prevent false operation of relay T due to the presence on a test wire of a booster battery metering condition.

If when the call distributor circuit is taken into use there is no Waiting call associated with the lamp display circuit but there is a free assigned connecting circuit, then the uniselector wipers are driven past the outlets to the display circuit and the control outlet and are not stopped (except possibly for the purpose of bringing about the operation of relay WS) until the outlet to such a connecting circuit is tested. The reason why the wipers are driven past all the queue-forming outlets is that in the circumstances stated the test-wire circuit of the outlet which at the time corresponds to the head of the queue is open at contact coi in the lamp display circuit (Fig. 4). In such circumstances the circuit in which relay T is operated when the outlet to a free assigned connecting circuit is tested is: earth via contact en! in the display circuit and a path in the assigned connecting circuit including the incoming S or supervisory wire thereof, bank contact and wiper 5 or 6, contacts w85, ssii, ds2 and b4, and so on.

In any case in which relay T is operated when the outlet to a free assigned connecting circuit is tested, the consequent operation of its auxiliary relay S brings about the operation of wiper switching relay SS, the operating circuit being earth, contact s, winding of the relay, resistance YD,'battery. Contact s6 makes the continued holding of relay WS if this is operated dependent on re-lay S instead of on relay B. Contact ssi closes a holding circuit for relay SS, contacts S82 and ss3 close points in the positive and negative wires on the outgoing side of repeating coil TR, contact ssll applies earth to the S wire of the connecting circuit, Contact s55 opens the ringing signal tone circuit, Contact ss connects earth to the incoming P wire, and contact ssl releases relay B and relay DS if this is operated and closes what may be an operating circuit for relay TC. If the calling line is an ordinary line and not a call oiiice line, relay TC operates in the circuit: earth, contact ss'l, winding (I) of the relay, resistance YE., battery, and closes a holding circuit for itself at contact tcl and completes the positive and negative speaking wire circuits at contacts tcZl and 03. If the calling line is a call office line, relay TC does not operate when front Contact ssl closes, since in this case incoming wire CO is earthed as it is connected to the relevant contact in the bank of wiper P5 (Fig. 1) of each of the associated line switches which are connected to call ofce lines. The earth is of course derived over contact h5 in the incoming line circuit which has taken the call distributor circuit into use. Wire CO is not connected to line switches associated with ordinarylines. When relay TC is prevented from operating at the time front contact ssi closes, the operator receives tone current from a source connected to wire DT, the path of the tone current including resistance YB and contacts rc2, ss2, s2, and w83, and wiper l or 2. The receipt of the tone signal notifies the operator that the calling line is a call oice line, and the operator thereupon throws a tone cut-off key in the position circuit which brings about the connection of earth to the negative wire. This earth connection operates relay TC on its winding (I) in the circuit which includes bank contact and wiper 3 or 4, contacts w-sfi, s3, ssii, and tc3, and the relay locks up and completes the positive and negative speaking wire circuits as previously described. The operation of relay SS places the holding of the connection under the joint control of the operator and the calling party, since relay SS when operated is held as long as either of contacts Z3 or sli remains closed and relay S is held dependent on relay T. The calling party can flash the operator when necessary, since intermittent operation of the switchhook causes intermittent operation of relay L with a consequent intermittent operation of contact l2 in the S or supervisory wire.

If the calling party clears iirst, as would normally be the case, the operator is informed of such clearing by the permanent change of condition of the relevant supervisory lamp which reyoni, [02, and b5. reached, relay WS is released since its holding sults from the opening of contact Z2. The operator can re-ring the calling party if necessary by throwing a ring key in the position circuit which brings about the connection of battery to the positive wire. Such connection of battery operates relay RR in av circuit which includes bank contact and wiper i or 2, contacts wist, s2, ss2, and to2, and upper righthand winding of repeating coil TR, and the relay at contacts rrl and 112 connects the incoming po-sitive and negative wires to a source of ringing current which is connected to wires RG and RT. When the calling party and the operator have both cleared, the uniselector is returned to normal by the closure of a homing circuit over contacts ssl, S5, oni, and b5. If relay WS is operated, it is released when the normal position is reached since its holding winding (II) is then short-circuited by contact 0712.

If the uniselector of the call distributor circuit fails to nd a' free assigned connecting circuit when it is caused to search for such a circuit, which condition may arise for example when two sruch uniselectors are simultaneously released from the overflow outlet associated with the lamp display circuit, then relay T operates to stop the Wipers when the last outlet but one in the banks of wipers 2, e, 6 and 8 is tested. The circuit for relay T in this case is earth over front contact ds2 or over bank contacts ds and ssii and front contact ws and wiper G, Contact bfi, rectifier, windings (I) and (II) of the relay, contact w85, wiper 8 and bank contact, contact Zoli, winding (I) of relay LC and non-inductive shunt, battery. Contact tl ychanges over and relay LC operates. Contact lol closes a circuit for holding relay LC on its winding (II) before contact Zoli opens the circuit of winding (I) contact lc2 opens the operating circuit of relay S and closes a point in a circuit for latch magnet LM, and contact Zo, releases relay DS if this is operated. Relay T releases immediately contact [c4 opens and replaces the short-circuit about relay S so that this relay is only operated momentarily if at all. The uniselector is thus returned to normal by the closure of a homing circuit over contacts ss'i, S5, When the normal position is winding (II) is then short-circuited by contact 0112, and relay LC is consequently released by the opening of contact w82. Ihe circuit is thus brought to the same condition as when it is first taken into use, and testing of the outlets in search of one marked as selectable again takes place.

Referring now to the lamp display circuit shown in Figs. 4 and 5 this is arranged to have a plurality of appearances in the banks of the switches of the distributor circuits (e. g. circuits such as the call distributor circuit shown in Fig. 3) with which it is .associate-d, some of the appearances corresponding to positions in a queue of waiting calls and one being provided for overflow purposes. The circuit actually provides for four appearances of the first-mentioned kind. The test wire of each appearance of the firstmentioned kind is connected via Wire Ti, T2, T3 or T4 as the case may be to one of a series of test-wire relays A, B, C,and D, and when none of these four relays is operated but the conditions are such that a queue is to be formed, a circuit is prepared for one of them over wipers RQ2 and RQ3 ofareverse drive step-by-step switch. When the test relay of the switch of one of the associated group of circuits operates in series with the test-Wire relay for which a circuit is thus prepared, the test-wire relay operates and locks up (over a contact such as al) and prepares a circuit for the next relay in the series (over a contact such as a2) and so on. The operation of a test- Wire relay closes or brings about the closure of a lamp'circuit determinedv by the position then occupied by the step-by-step switch, the number of lamp circuits so completed indicating the number of calls waiting in the queue, and also completes a circuit for slowly charging a condenser via a high resistance. The lamp display circuit shown in the drawings provides o' course for the control of four lamps circuits, since by having four test- Wire relays it provides for a queue having up to four calls in it. The actual lamps are not shown in the drawingsbut are either connected to wires LI, L2, L3, and L4 or are controlled by auxiliary relays connected to these wires. In any case the application of earth to one of the wires means the completion of the corresponding lamp circuit. For convenience the wires will hereinafter be referred to as lamp wires. There are a condenser and a high resistance corresponding to each testwire relay, and it is arranged that the release of a test-wire relay connects a discharge path across the corresponding condenser, Condenser QA and high resistance YP correspond to relay A, condenser QB and high resistance YQ correspond to relay B, condenser QC and high resistance YR correspond to relay C, and condenser QD and high resistance YS correspond to relay D. Each condenser may have a capacity of l micro-farads and each high resistance may have a value of 4 megohms. The discharge path resistances YD, YE', YF and YG may each, have a Value of 200 ohms. A typical path for the operation of a testwire relay is wire TJ, winding of relay A and the resistance connected in parallel therewith, bank contact and wiper RQZ, contacts col and .#3, wiper RQ3 and bank contact, and resistance YH. A typical circuit for slowly charging one of the condensers QA, QB, QC, and QD is battery, high resistance YP, condenser QA, front contact a4,'tapping on potentiometer -formed by resistances YA and YB and the heater of a pentode valve VA. It should be noted that owing to the use of the potentiometer arrangement, the charging potential is less than the normal exchange voltage. A typical circuit for applying earth to one of the lamp wires is earth, contact a3, wiper RQ4 and bank contact, wire LI.

When the lamp circuit corresponding to the head of the queue becomes closed, i. e. when lamp wire LI is earthed, relay AC is operated and so also is relay EN unless it is valready operated due to prior energisation of its winding (II). The circuit for operating relay AC includes Contact st5. Contact cc! closes a holding circuit for relay AC, contact acZ prepares a circuit for relay AM, contact ac3 prepares a circuit for the stepping magnet DM of the step-by-step switch, Contact ac prepares a holding circuit for relay ST and contact co5 prepares an operating circuit for relay ST. Contact en! when operated removes earth :from wire CM, and contact e113 when operated short-circuits winding (II) of relay OF. Wire CM is connected to all the connecting circuits to which the distributor switches have access, and the removal of the earth from this wire causes all the connecting circuits to appear unselectable to a searching distributor switch which has not been in the queue. Contact ent when operated disconnects the control grid of the pentode valve VA from the negative pole of battery (to which it is normally connected via a. resistance YN) and connects it to contact cm2. It is arranged that with contact end operated and contact cm2 unoperated the potential of the control grid is such that relay AN included in the anode circuit is operated. While relay AN is operated it, at its contact ani, keeps open a point in the short-circuit which normally exists about relay AM so that this latter relay is operated and released with operation and release of contact a02. When relay AM is operated, contact ami opens another point in the said shortcircuit and prepares a circuit for relay DC, and contact cm2 eiects a further change in the connection of the control grid of the pentode. With the new connection the control grid is connected via wiper RQB of the step-by-step switch to the junction of the condenser and high resistance associated with the test-wire relay which is associated with the head of the queue at the time being considered. The connections are such that the said junction becomes more negative as the condenser becomes more fully charged, and the rate at which each condenser is charged and the sensitivity of the anode circuit relay AN are arranged to be of such values that the relay is released if at any time the condition arises that the call at the head of the queue has been waiting for more than a predetermined period. When such release of relay AN occurs, relay DC is operated in a circuit over contacts ac2, anl, and ami, and at contact del connects earth to wire OM2 to give a control signal to one or more omnibus operators positions. The control signal either causes the omnibus positions to assist in dealing with the calls in the queue or, if the omnibus positions are already dealing with such calls, prevents other classes of call being displayed at these positions. It should be noted that relay AN is energised to a predetermined degree before being put under the control of a condenser-resistance time-measuring combination, which ensures that its release will take place at a denite energisation. It should also be noted that the fact that the control grid of the pentode VA is normally connected to the negative pole of battery so that no appreciable anode current flows ensures a long life for the valve.

When the number of calls waiting in the queue reaches a predetermined ligure (e. g. when the number of calls waiting in the queue becomes three) relay OM is operated when earth is applied to the lamp Wire (e. g. wire L3) corresponding to the last position in the queue comprising this predetermined number of calls, its operating circuit including the lamp wire, a cross-connectionv between this wire and wire OMS, and winding (I) vof the relay. Relay OM on operation locks up on its winding (II) in a circuit over wire OMA and a cross-connection between this wire and a lamp wire (e. g. wire LZ) corresponding to a position in the queue earlier than the position just referred to, and at contact cm2 earths wire CM2 if this is not already being done by contact dci. As previously described, the connection of earth to wire OMZ gives a control signal to one or more omnibus operators positions.

When the number of calls waiting in the queue becomes the maximum for which provision is made (i. e. becomes four), slow releasing relay OF is operated on its Winding (I) consequent on the application of earth to lamp wire L4, and at contact oft completes the testing-in circuit of the overflow appearances of the display circuit in the banks of the distributor switches.

Wire

Cl is connected to test-Wire resistances such as YG in Fig. 3 and wire Ml is connected to battery via an overflow meter.

When an operator assigns a free connecting circuit for use While calls are waiting in the queue, relay ST is operated onits winding (I) by the application of earth to wire RC at the operators position circuit. The relay on operation locks up on its vwinding (II) in a circuit over contacts StZ and 0.04, and at contact stl opens its operating circuit and makes itself slow to release by short-circuiting its winding (I). During the make through period of makebefore break contact stl, battery via resistance YC (which has a comparatively 10W ohmic value) brings about operations in the position circuit which result in the removal of the earth starting signal from wire RC. Contact st3 connects earth over contact a'c2 to Wiper RQ2 and thereby short-circuits both the test-wire relay which is associated with the head of the queue at the time and the distributor test relay which has been held operated in series therewith. Contact std energises the stepping magnet DM of the step-bystep switch. The distributor test relay releases and the distributor leaves the queue and searches for the assigned connecting circuit. On the release of the short-circuited test-wire relay, the corresponding condenser is disconnected from the charging circuit inwhich it has been connected and is discharged through the associated one of the resistances YD, YE, YF, and YG,' and relay AC is released by the removal of earth from lamp wire LI. The opening of contact a02 releases relay AM and also relay DC if this is operated, the opening of contact ac3 de-energises the stepping magnet DM so that wipers RQI-RQS take one step, and the opening of contact ac releases relay ST. The operating circuit of relay ST is opened at contact acti.v If there is a further call in the queue, relay EN remains held while all these operations are taking place on its windings (II) and (I) in turn, relay AN is again energised to a predeterminedV degree due to the connection of the control grid of valve VA in a circuit over front contact en4 and back contact (mm2, and lamp wire LI is again earthed as soon as the wipers have completed the step referred to. Such earthing of lamp wire Ll brings about a further operation of relays AC and AM and possibly DC, and the circuit then awaits the iurther application of a start condition toY Wire RC.

'When an operator assigns' a free connecting circuit for use at a time when no calls are waiting in the queue, relay CO is operated over back contact e112 consequent on the earthing of'wire RC and at its contact col opens the test-wire relay operating circuit which is prepared at the time. This has the elTect or causing a call distributor switch to drive past the outlets to the display circuit as previously described in connection with the circuit of Figs. 2 and 3.

When there are no calls in the queue (and relay EN is consequently unoperated),r the stepping switch can be caused to drive continuously for testing purposes by placing a loop across the two contacts of test jack TJ. Relay OF operates on its winding (II) during such testing and completes the testing-in circuit of the overflow appearances of the display circuit in the banks of the distributor switches.

Referring now to the bothway line circuit shown in Figs. 6 and 7 it will be understood that the circuit is arranged so that, when alternating calling current (e. g. ringing current) is received over the line connected to the positive and negative wires shown incoming on the left of Fig. 6 and the motor-driven uniselector which forms the distributor switch is consequently caused to test its outlets in search of one marked as selectable, the rst outlets tested are those to connecting circuits on a special transfer position. Then come in turn an overflow outlet associated with the lamp display circuit, the queue-forming outlets to the lamp display circuit, a control outlet, and outlets to connecting circuits at ordinary operators positions. The arrangements are such that when the bothway line is extended to an ordinary position it is possible for the operator thereat to transfer the call concerned to the special transfer position. The lamp CL and key AK shown in a broken line rectangle in Fig. 6 are individual to the bothway line and are situated on the special transfer position. The P (or private), positive, negative, and S (or supervisory) wires shown incoming at the top of Fig. 7 form the path of entry to the line circuit for an outgoing call.

The motor-driven uniselector which forms the distributor switch operates at a high speed and has Wipers l-. It is similar to the uniselector shown in and described with reference to Fig. 3. The latch magnet is designated LM and has a magnet alarm relay RA in series with it. The wipers of the uniselector are divided into two sets, the set connected in circuit at any moment depending on the condition of a wiper choosing relay WS. Contacts onl and on?! are oit-normal contacts of the uniselector. Relay RA is operated whenever the latch magnet is operated, and at contact ral connects alarm lamp AL between battery and Wire IEW which is connected to interrupted earth. Contact m2 places a guarding earth on the private wire of the path of entry to the circuit for an outgoing call (unless thisvwire is already earthed at one of the other contacts associated with it), contact m3 opens a point in the circuit'for` applying earth to Wire GCW and earths wire RAW leading to an alarm circuit, and contact m4 closes a point in a holding circuit for relays SS and TC'.

When alternating calling current (e. g. ringing current) is received over the bothway line, it takes effect on a suitable call responsive device connected to wires RRW. The said device operates and earths wire STW, thereby in normal circum-y stances operating relay ST in a circuit over contacts gs! and ssl, contact of night switching key NSK, and contacts tc, S86, and ws. Contacts stl and stl close a holding circuit for relay ST, contact stZ connects a busying earth to the private wire of the path of entry to the circuit for an outgoing call, and contact st3 opens one circuit applying earth to wire GCW. Wire GCW is connected to a group control circuit and is normally earthed over contacts in each line circuit of the group concerned. Contact st closes the circuit of latch magnet LM and contact stt closes a point in the circuit or high-speed test relay T. The circuit for latch magnet LM is earth, contacts tl, si, Zc4, U5, and st, winding of the magnet, winding of relay RA, battery. The call responsive device referred to only applies earth to wire STW for the period for which the alternating calling current persists.

As previously stated, the rst outlets tested when the wipers of the uniselector are thus set in motion are those to connecting circuits on the special transfer position. Normally such outlets do not provide an operating circuit for test relay T, and rotation of the wipers continues at least until the overflow outlet associated with the lamp display circuit is reached. Test relay T is only operated with the wipers on this overflow outlet when all the queue-forming outlets to the lamp display circuit are engaged. When relay T is so operated, its operating circuit is earth, contact tc4, bank contact and wiper 5, contacts w34, ssii, ds2, m13, and st, dry-plate rectifier, windings (I) and (II) of the relay, contacts tid and 0,114 in parallel, contact w55, wiper 'l and bank contact, resistance YG, battery via an cverow meter connected at the time to wire Cl in the lamp display circuit (Fig. 4). In these: circumstances, the changing over of contact tl inserts the winding of relay S in series with latch magnet LM so that this relay is operated and the latch magnet is released due to the resistance of the relay winding. Such operation of relay S has however little material effect. Contact si closes an alternative circuit for `the relay over resistance YB and de-energises the latch magnet, and contact s2 connects earth to the junction of resistance YA and winding (I) of relay TC to prevent relays SS and TC being operated by the closure of front Contact S5. The 'test relay T and auxiliary relay S are released and the wipers of the uniseleotor again set in motion as soon as a position in the queue becomes vacant, relay T being released by the opening of the circuit of its holding winding (II) at contact of! in the larnp display circuit (Fig. 4).

The circuit in which relay T is operated to bring the wipers to rest on a queue-forming outlet is earth, contact tot, bank contact and wiper 5, contacts wsll, ssll, ds2, cm3, and stt, dry-plate rectiewindings (I) and (II) of the relay, contacts tft and ma in parallel, contact ws, wiper 'l and bank contact, battery connected at the time (via certain apparatus) to one of the wires 'Ti- T4 in the lamp display circuit (Fig. fl). When relay T is so operated, the changing over of contact ti inserts the winding of relay S in series with the latch magnet and short-circuits the high-resistance winding (I) of relay T and the associated rectifier, thereby marking the outlet engaged. and bringing about the operation of the test-Wire relay in the display circuit. Relay S operates and at contact s2 closes an operating circuit for relay TC, this circuit being earth, contacts $32, s2, and w52, wiper i and bank contact, winding (I) of the rela resistance YA, battery. Relay TC locks up in a circuit over contacts des, tcl and stl `Contact tot opens the testing circuits of the overflow and queue-forming outlets to the lamp display circuit, and contact fc5 prepares a circuit for stop-ping the wipers on the control outlet previously referred to.

When subsequent to this relay 'I' and S are released due to the earthing of the relevant test wire in the display circuit, (which earthing signies that the call is at the head of the queue and that there is a free assigned connecting circuit), the wipers are again set in motion but are stopped by the operation of relay T as soon as the control. outlet is reached. vThe circuit in which relay T is operated in this case is earth, bank contact and wiper 5, contacts weil, ssii, m3, and st, rectifier, windings (I) and (II) of the relay, contacts tf and and. in parallel, contact w35, wiper 'i and bank contact, Contact tc, winding (I) of relay DS and non-inductive chu' battery. The changing over of contact ti brings about the operation of the relay S usual and also operates relay DS. Relay DS locks up on its winding (II) in a circuit over contacts dsl, Zc2 and S35, and a contact ds? renders the uniselector testing circuit independent of wipers 5 and and at contact s3 releases relay TC. A short-circuit over contact si. and wiper l prevents relay SS and winding (I) of relay TC being energised due to the closure of front contact S5. The opening of contact tc5 brings about the release of test relay T and its auxiliary S, and further rotation of the wipers ensues until either the outlet to a free assigned connecting circuit in the banks of wipers I, 3, 5, and l is reached or until the last position prior to normal is reached. It should be noted that the bank contacts engaged by the wipers of the uniselector in this position are not used for outlets to connecting circuits. If the said last position is reached during such a search, the wipers are stopped by the operation of relay T in the circuit: earth, contacts ds, cm3, and st, rectier, windings (I) and (II) of the relay, contacts tf1! and ont in parallel, Contact w35, wiper 'I and bank contact, winding (I) of wiper choosing relay WS and non-inductive shunt, battery. Relay WS is operated when contact t! changes over, and locks up on its winding (II). and connects up the alternative set of wipers of the uniselector. Contact ws! makes before the back contacts of the relay open. The changing over or" contact 2oo5 releases relay T and further rotation of the wipers ensues, the outlets tested during such further rotation being those connected to the bank contacts associated with the alternative wiper set. The wipers pass through normal at a speed which is suiiiciently high to prevent relay IVS from being released by the momentary closure of contact 011,2.

In either of the two cases just mentioned, when the outlet to a free assigned connecting circuit is tested, the wipers are stopped by the operation of relay Tin the circuit: earth, contacts 0332, cm3 and stt. rectier, windings (I) and (II) of the relay, contacts hfi and and in parallel, contact w35, wiper l or 8 and bank contact, battery connected to the P wire of the connecting circuit. 'Ihe rectier serves to prevent false operation of relay 'I' due to the presence on a test wire of a booster battery metering condition.

If when the bothway line circuit is taken into use there is no waiting call associated with the lamp display circuit but there is a free assigned connecting circuit, then in normal circumstances the uniselector wipers are driven past the outlets to the display circuit and the control outlet and are stopped (except possibly for the purpose of bringing about the operation ci relay WS) until the outlet to such a connecting circuit is tested. The reason why the wipers are riven past all the queue-forming outlets is that in the circumstances stated the test-wire circuit of the outlet which at the time corresponds to the head of the queue is open at contact coi in the lampA display circuit (Fig. 4f). In such circumstances the circuit in which relay T is operated when the outlet to a free assigned connecting circuit is tested is:- earth via contact cui in the display circuit and a path in the assigned connecting circuit including the incoming S or supervisory wire thereof, bank contact and wiper 5 or 6, contacts wed, est, del, rmi?, stt, and so on.

In any case in which relay T is operated when the outlet to a free connecting circuit is tested, the consequent operation of its auxiliary relay S brings about the operation of relays SS and TC, the operating circuit being: earth, contact e5, winding of rela] SS, winding (I) of relay TC, resistance YA, battery. Relay SS is the Wiper switching relay. Contacts S52 and S33 close points in the positive and negative wires on the outgoing side of line condensers QA and QB, Contact ssii connects earth via the winding of relay SY to the S wire of the connecting circuit, contact s55 releases relay DS if this is operated, and Contact S35 releases relay ST. Contact to2 maintains an engaging earth on the private wire of the path of entry to the circuit for an outgoing call, and contact rc3 prevents the falling back of contact s't3 from app-lying earth to wire GCW. The through connection thus set up is held under the control of the operator.

The calling party can bring about a hashing of the operator when necessary by again momentarily applying alternating calling current to the line and thus causing the call responsive device again to apply earth to wire STW. Such earthing of wire STW operates relay Z in a circuit over contacts gsi and ssl. Relay Z on operation locks up over contacts al, syl and siii and at contact a2 applies an interrupted earth condition to the S Wire of the connecting circuit, thereby flashing the operators supervisory lamp. When the operator responds by throwing' the speak key, the resistance of the S wire circuit is.

reduced so that relay SY operates and at its contact syl releases relay Z.

If the operator controlling the connecting circuit Wishes to re-ring the calling party after this party has cleared, a ring key in the position circuit is operated to bring about the connection of battery to the positive wire. Such connection of battery operates relay RR in a circuit which includes bank contact and wiper l or 2, contacts w82, s2, and S82, and winding (I) of retard coil R, and the relay at contacts Mi and W2 connects the incoming positive and negative Wires to a source of ringing current which is connected to Wires RG and R'I. When the operato-r controlling the connecting circuit clears, the uniselector is returned to normal by the closure of a homing circuit over contacts oni, and 5755. Relay SS and TC are held operated until the normal position is reached by a circuit over contacts m4 and ssl. If relay WS is operated, it is released when the normal position is reached since its holding winding (II) is then short-circuited by Contact mi2.

If the uniselector of the bothway line circuit fails to find a free assigned connecting circuit when it is caused to search for such a circuit, which condition may arise for example when two such uniselectors are simultaneously released from the overflow outlet associated with the lamp display circuit, then relay T operates to stop the wipers when the last outlet but one in the banks of wipers 2, 4, and 8 is tested. The circuit for relay T in this case is earth over front contact ds? or over back contacts ds? and ssd and front contact wist and Wiper t, contacts mz3 and stt, rectifier, windings (I) and (II) of the relay, conv tacts tfil and and; in parallel, contact w55, wiper t and bank contact, contact lc3, winding (I) of relay LC and non-inductive shunt, battery. Contact ti changes over and relay LC operates. Contact Zcl closes a circuit for holding relay LC on its winding (II) before contact ZcS opens the circuit of winding (I) contact Zc2 releases relay DS if this is operated, and contact lcd opens the operating circuit of relay S and closes a point in a circuit for latch magnet LM. Relay T releases immediately contact Zc3 opens and replaces the short-circuit about relay S so that this relay is only operated momentarily if at all. The uniselector is thus returned to normal by the closure of a homing circuit over contacts S5, opl, lcd, tf5, and st. When the normal position is reached, relay WS is released since its holding winding (II) is then short-circuited by Contact 0112, and relay LC is consequently released by the opening of contact wsl. The circuit is thus brought to the same condition as when it is iirst taken into use, and testing of the outlets in search of one marked as selectable again takes place.

As previously stated, the bothway line circuit is arranged so that when the line is extended to an ordinary position in the manner which has been described it is possible for the operator thereat to transfer the call concerned to the special transfer position. To bring about such transfer the operator controlling the connecting circuit to which the call has been extended throws a transfer key in the position circuit, it being arranged that this action brings about the connection of battery to the negative wire so that relay TF operates on its winding (I) in a circuit which includes bank contact and wiper 3 or 4, contacts w53, s3, and S33, and winding (II) of retard coil R. Relay TF locks up on its winding (II) in a circuit over contacts tfl and stl, and at contact tft closes a circuit over contact cm2 for lighting the calling lamp CL on the transfer position. The operator at the transfer position accepts the call by assigning for use a free one ofthe connecting circuits associated with this position and operating the answering key AK individual to the bothway line. Relay AN in the line circuit is thereby operated on its winding (I) and locks up on its winding (II) in a circuit over contacts ani, m2, and tf. The opening of back contact m2 extinguishes the calling lamp CL, contact cm3 makes the uniselector testing circuit independent of wipers 5 and 6, and contact and releases relay T. The release of relay T is of course followed by the release of relay S. The falling back of contact S5 closes a homing circuit for the uniselector, this circuit being one which includes contacts oni and st5. When the wipers reach the normal position, relays TC and SS are released on the opening of contact raf! and relay WS is also released. A circuit for operating relay ST is consequently closed over contacts tf, m2, fc5, ssii, and w36. Relay ST operates and locks up over front contact sti. The opening of back Contact sti releases relayTF, and a circuit for the latch magnet is consequently closed over contacts ti, sl, Zoli, 1.75, and st and search for the outlet to the assigned connecting circuit ensues, When this outlet is tested, the Wipers are stopped by the operation of relay T in the circuit: earth, contacts (m3 and stt, rectifier, windings (I) and (II) of the relay, contacts tf, and w55, wiper I and bank contact, battery connected to the P wire of the connecting circuit. The operation of relay T is followed as usual by the operation of relay S and contact S5 operates relays SS and TC. Except that the opening of contact to@ releases relay AN, subsequent operations in the line circuit are the same as in the case where an outlet to a connecting circuit at an ordinary position is seized.

At times when the night switching key NSK is operated, the earthing of wire STW on the initiation of an incoming call operates relay TF on its winding (II) and Contact tf lights calling lamp CL. The call is consequently handled from then onwards in the same manner as a transferred call.

When the bothway line circuit is taken into use for a call outgoing over the line, relay GS is operated over the private wire of the appropriate path of entry. Contacts asl and gs2 prepare operating and holding circuits for relay Z so that the party at the distant end can if desired flash the operator who has taken the line into use, Contact gsS opens a point in the circuit applying earth to wire GCW, and contact Q84 lights lamp AL if lamp control switch LCS is closed.

We claim:

1. In a telephone system wherein successive calls are stored until a free connecting path is available, means for automatically withdrawing the calls from storage and extending them over free connecting paths in the same order in which they were stored, a plurality of timing devices, means for associating a timing device with each stored call, a special signal, means in a timing device operated during association with a stored call for producing a continual change therein, and means operative in response to a certain degree of change in the associated timing device for causing said signal to indicate that a call has been waiting for a predetermined time.

2. In a telephone system wherein successive calls are stored until a free connecting path is available, means, for automatically withdrawing the calls from storage and extending them over free connecting paths in the same order in which they were stored, a plurality of timing devices, means for associating a timing device with each stored call, a special signal, means in a timing device operated during the association with a stored call for causing a continual change in a potential controlled thereby, and means operated in response to said changed potential for causing said signal to indicate that a stored call has been waiting for a predetermined time.

3. In a system as claimed in claim 2, in which said last named means comprises a thermionic v valve including a grid with said controlled potential applied thereto and a relay controlled by the anode current of said valve for giving an indication to said signal.

4. In a system as claimed in claim 1, the provision of means for associating said last named means, with the timing devices in turn.

5. A system as claimed in claim 1, in which each of said timing devices comprises a condenser with a charging circuit including a resistance and means for closing said circuit to render said device operative.

6. A system as claimed in claim 2, in which said last named means is effective when a certain potential is applied thereto for giving an indication to said signal.

'7. In a system as claimed in claim 1, means associated with the timing devices for controlling the rate of said continual change therein.

8.4In a telephone system wherein successive calls are stored until a free connecting path is available, a sequence arrangement including a plurality of timing devices, means for associating a timing device with each stored call, a special signal, said timing device comprises a condenser with means for continually varying a potential there-across at times when an associated call is waiting, means for giving an indication to said signal when a stored call has been waiting for a predetermined time, said means including a thermionic valve having its control grid associated with the varying potential across said condenser, and a relay controlled by the anode current of said valve for giving said indication.

9. A system as claimed in claim 8, in which said thermionic Valve is maintained in operating condition at all times, and means whereby the control grid is normally maintained at a potential negative with respect to the cathode so that no appreciable anode current ows.

l0. A system as claimed in claim 8, in which the varying potential across said conductor is produced during charging of the condenser, and means including a potentiometer for determining the charging potential.

11. In a telephone system having call storage facilities from which stored calls are issued automatically in the order in which they were stored as connecting paths become available, a plurality of timing devices, one of said devices associated with each stored call responsive to the storing thereof, and means. in each device for producing a continual change therein during its association with a stored call, thereby to characterize each call independently of the others in accordance with the length of time said call has been in storage. l.

12. In a system as claimed in claim 11, wherein the stored calls form a queue, and wherein each stored call arrives in turn at the head of the queue as the calls preceding it in the queue are issued from storage, signalling means associated with each call responsive to that call arriving at the head of the queue and operated if that call has been in storage for a predetermined interval of time.

13. In a system as claimed in claim 11, means for controlling the rate of said continual change in said devices.

14. In a telephone system having call storage facilities from which stored calls are issued automatically in the order in which they were stored as connecting paths become available, a plurality of timing devices, one of said devices associated with each call responsive to the storing thereof, signalling means controlled by the associated timing device and operable to indicate that a call has been stored for a certain time, and means for Varying the length of time which a call must have been stored before said signalling means is operated.

15. In a telephone system wherein calls are stored until free connecting paths are available for their extension, a timing device associated with a stored call, said device comprising a condenser with means for continually varying the potential there-across while said call is in storage, a thermionic valve having its control grid associated with the varying potential across said condenser, and a relay controlled by the anode current of said valve and operated when the call has been stored for a predetermined interval of time.

BERNARD ANTHONY I-IENSLER. HORACE EDGAR I-IUMPI-IRIES.

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