US1545183A - Telephone system - Google Patents

Description

July 7, 1925.

' E. E; CLEMENT Tannrnous sxsrsu Filed June 5, 1905 2 Sheets-Sheet 1 July 7, 1925.

E. E. CLEMENT TELEPHONE SYSTEM 2 Sheets-Sheet 2 wuuma Patented July 7, 1925.

UNITED STATES PATENT OFFICE.

EDWARD E. CLEMENT, OF WAfiHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR, BY MESNE ASSIGNMENTS, TO THE NORTH ELECTRIC MANUFACTURING COMPANY, A

CORPORATION OF OHIO.

TELEPHONE SYSTEMI.

Application filed June 5, 1905. Serial No. 268,784.

To all whom it may concern:

Be it known that I, EDWARD E. CLEMENT, a citizen of the United States, residing at lVashingto-n, in the District of Columbia, have invented a certain new and useful Improveinent in Telephone Systems, of which the following is a specification, reference being had therein to the accompanying drawing.

My invention relates to telephone exchange systems, and constitutes an improvement in that type of systems which I have denominated semi-automatic, wherein a connection is initiated by an operator, manually, and is completed through the medium of mechanism controlled from the subscribers station. The object of the invention is to produce a circuit of the two-wire type, which will enable existing installations equipped with manual apparatus to be remodeled and their capacity increased by the addition of automatic apparatus without substantial change in the manual portions, or in the circuits.

While, as I have stated, the invention has to do particularly with semi-automatic systems, I contemplate applying the principles involved to full automatic installations, in a manner which will be pointed out in the detailed description and statement of oper ation.

Briefly stated. the present scheme involves the use of a plain metallic circuit throughout, all operations of talking, and signalling being conducted over or controlled through this circuit. All working impulses for signalling and switching are sent over one side of the circuit only, the working magnets being sensitive or quickly responsive, and a control magnet of sluggish nature responding to long makes or long breaks to bring the various pieces of apparatus into circuit in required sequence. This control magnet, actuating a suitable switching device, takes the place of the usual so-called side switch in automatic systems.

My invention is illustrated in the accompanying drawings, wherein Figure 1 is a diagram showing a subscribers line and an operators connective circuit. Figure 2 is a diagram constituting a continuation of Figure 1, showing a switch trunk and another subscribers line.

Fiiure 3 is a plan View of the pilot switc Figure 4 is a side view of the magnet and ratchet.

Referring to Figure 1, A is a subscrihers station equipped with the usual transmitter T, receiver R, switch-hook H, condenser C and ringer Q. This station is connected to the central oflice by line-wires 12', terminating in relay contacts m, m of the cutoff relay N. These contacts are normally in engagement with other contacts n, a, the first connected by wire 5 through relay M to the main battery B, and the second to ground. The contacts n, n are taken away from their normal resting contacts where the relay N is excited, and brought into engagement with other contacts n n, connected to the line jack J, in the spring and sleeve sides of the same, through the wires 3-4, and also through wires 7-8 to the multiple contacts J which are disposed in automatic switches.

The cord-circuit shown terminates in an answering-plug P and a calling-plug P, each with tip and sleeve contacts p, 1), connected through cord conductors 911, 10-12, broken by condensers C, C. The main battery B is bridged across each end of the cord through a pair of relays. On the answering end the controlled relay S is between the battery and the sleeve side, and

the supervisory relay S between the battery and the tip side, the former being a front contact relay and the latter a back contact relay. These two relays jointly control the local circuit of the superviwry lamp 8. On the calling end of the cord the arrangement is the same, the controlled relay S and the supervisory relay S jointly governing the circuit of the supervisory lamp 3 In the callingend of the cord is also included the ringing key K, which may be provided with listening contacts, if desired, but in the present system is not so shown.

So far, the circuits and apparatus are all of a well-known type, and as I describe my additions thereto it will appear that this much, which is the essential and distinguishing part of the manual system, remains unchanged. I add to but do not alter the cord or line-circuit. In a multiple-switchboard the wires 3-4 are connected to the minitiple-jacks through the branches 7.-8; and here the first difl'erence occurs, for I discard the multiple jacks, and substitute the terminals J in the banks of the switches.

At the subscribers station it is necessary to provide some means for sending impulses in predetermined order. These all go over the No. 1 side of line, hence it is possible to make and break the circuit manually, or to use an automatic sender such as the regular standard automatic electric sender in common use with the so-called Strowger systems. In fact it is entirely possible to use the ordinary switch-hook without any change whatever. This is manipulated to send successive short breaks in groups, leaving the line closed for an appreciable time between the groups, the number of breaks in each group corresponding to a digit of the number wanted. Thus in sending the number 4436, the subscriber would remove his receiver from the hook, and listen. In Figure 1 I have shown the special variable tone generator G connected through a condenser C to the wire 5, so that as long as the line is connected to the line-relay M a characteristic sound will be produced in the subscribers receiver. Even without this, however, the subscriber can tell when the plug is inserted, because it the circuits are traced it will be found the battery is reversely connected to line when the plug P is inserted. Having waited until he hears the plug inserted, knowing this either by the cessation of sound from generator G or by hearing the loud click due to the bat tery reversal, the subscriber taps his hook sharply and rapidly four times, then after a short interval during which it remains up he taps it four times more. As soon as he has done this he will hear the battery cut off by the opening of contacts 2 2 in the side switch, and he will then wait until battery comes on again, in the meantime if the generator G is employed the tone signal becoming audible, inasmuch as the cut-off relay N has lost its current. IVhen the plug P is inserted in the trunk jack J the relay S pulls up, the side switch Z moves forward a step, and the contacts 2' .2 are again closed, whereby magnet N again takes current, relay M and generator G or reversed battery B are cut ofi', and the subscriber knows he can go ahead. He then taps the hook three times, and after an interval six times. The description of this operation sounds somewhat involved, but really it is simple in the extreme. The subscriber has only to remember that when he hears the musical note of generator G he must wait until it ceases before he can signal. It almost goes without saying that a phonograph might be substituted for generator G giving oral instructions.

I believe I am the first to produce a metallic circuit automatic system wherein only the standard subscribers instrument, line circuit, and switchboard apparatus are employed; I am also the first in any kind of a system, so I believe, to use an ordinary telephone set without an automatic sender, by manipulating the hookswitch.

In Figure 1 I and W are two sending wheels, or two pairs of sending wheels, the one, VV', adapted to be set by the subscriber independently to the desired thousands and hundreds digits; the other W adapted to be similarly set to the desired tens and units digits. These two pairs of wheels, as well as the cams, 10 and w and the detent wheel, 00, with its magnet, IV, are housed in a casing adapted to be clamped or other wise secured to any common battery telephone. The wheels named are preferably all on the same shaft, or on separate shafts geared together, and all the parts are shown in the figure in their normal or idle position. When the wheels have been set a handle is turned whereby the spring of a clockwork train is wound, and the detent on the armature, a, of the magnet, W, then retains the signal. The cam, 10 turns with the wheels. W, coming into the position shown, with the spring, 10 resting in its notch, when the thousands and hundreds wheels have run down. The cam, 1.0 on the other hand, runs with the wheels, W and comes to zero with them, after the units and tens have been sent.

The magnet, W, releases the train when it is energized, and opens the signalling circuit to line through the branch 58.

Associated with the cord-circuit is an indicator shown as comprising two step-by-step discs, each adapted to be set around by a magnet I or I, a retaining pawl being provided for each disc, and a restoring device, I The indicator magnets, I, I are each grounded on one side, and are connected back through wires 22 and 220 to the contacts 2 and .2 of the control or pilot switch, Z.

The shitting or pilot switch Z consists of a spindle with a ratchet wheel and a magnet to turn the same, the latter being shown at Z, and the movement substantially the same in kind as in the indicator. This ratchet wheel is held at each step by a detent pawl. which may conveniently be released at the end of a conversation either by the samemanually operated button, I which releases the indicators. or by an electro-magnet. The operation of this switch is shown in Figures 3 and 4. On the spindle of this switch are mounted arms or a cam drum. sweeping over contacts step-by-step as the ratchet wheel is turned. These contacts are shown in Figure 1 in pairs, supposed to be opened and closed successively as the cam drum is turned. At the first step the pair 2 2 is closed. to cut in the thousands indicator magnet. I; at the next step this pair is opened and the next pair, 2 z" is closed to cut in the hundreds indicator magnet, I; at the next step this pair is broken, and the next pair, 2 2* is closed to connect the battery wire 240 by way of wires 17 and 21 to the conductor 11 and so through the tip of the plug to the tip side of the switch trunk, so as to repeat the following impulses around the condenser, G, into the trunk circuit; this same step opens the battery circuit through wire 14 by opening the contact pair, 2 2 which is normally closed. There is then one more step to this switch, by which the pair 2 z are again closed and the pair 2 2 left closed. The final step or restoration then preferably cuts off the wire 21, although this is not absolutely essential, as during conver sation the magnet, S would form a shunt for the other grounded connections. It is better, however, to give the side switch the final step, leaving the pair, .2 2 closed and all the other pairs open, so as to have a clean cord-circuit.

Referring now to Figure 2, J is one of a group of trunk jacks located in front of each 0 rator, each trunk line, 31 and 32, prefera 1y appearing on a jack J in multiple at every section of the switch-board. The trunk comprises two wires 31 and 32, the former normally open everywhere, the latter connected only through the relay S to ground. When a plug is inserted in a trunk jack the magnet S gets current through the sleeve side of cord and magnet S and pulling up closes the ti side 31 of the trunk to relay S and grou'n Impulses coming over the tip side thereafter affect this relay,

which corresponds to the supervisory relay S of the cord-circuit. Each trunk is provided with a side or pilot switch by manipulation of which the different pieces of apparatus are succesively brought into proper relation with the relay S and other parts of the circuits and apparatus, as will be fully explained in a moment. This switch is designated for convenience Z", and is in every respect similar to the switch Z in the cord circuit. Each of these switches has an operating magnet for stepping its arm around a step at a time, this marked Z in the cord circuit, Figure 1, and Z in the trunk circuit, Figure 2. Each switch is controlled by a solenoid or other slow relay S which is quick to be energized and pull up its arma ture or core, but very slow to fall back and close the circuit of the stepping magnet. This sluggish action is accomplished by means of a noninductive shunt circuit (66 in Figure 1, 99 in Figure 2), around the relay Z and S", respectively. This solenoid or slow magnet is marked Z in Figure 1. and S in Figure 2. Each switch has a spindle and an arm or arms and contacts, as already set forth.

The trunk line til-+32 (Figure 2) has for its terminal a Selective switch P through which the connection initiated by the operator with plugs P and P, may be completed. This switch may be of any well known or usual ty e in which two motions or two selective di erentiating acts are employed. Such a switch is shown in Letters Patent 815,176, granted to Keith and Erick son, March 13, 1906.

l have shown the terminal contacts of the switch at 29 p and have indi-cateo the spindle at s". The multiple line-contacts are shown at J The trunk wires 31 and pass to contacts 3 and 7 being also connected to contarts 2 and These contacts are normally open, the former pair being controlled by the test relay Y and the latter by the pilot switch Z". The wipers 39 p are connected back by wires and 34 to the con tacts 3 3 of the test relay. normally touching the generator contacts 2 3 and wires 33 and are also connected to the contacts and 2 of the pilot switch. At a point between the generator G and the sleeve-side wiper 39 the wire 45 is connected to a choke coil to the main battery B, this being for the purpose of holding up the cut-off relay N while ringing. A busy-back generator G, preferably working through a condenser is connected across the contacts y, y of the test relay, these contacts being crossed together with the contacts 1 and y when the relay Y is energized, but insulated from the contacts 3 and y.

X is the release magnet. for the switch, and is connected from ground by wire 42 to the Contact 2" of the pilot switch. The generator circuit 45-46 also passes through a pair of contacts 2 2, and the test relay circuit 43-44 passes through a similar pair 2 2 of the pilot switch.

At the righthand end of Figure 2 is shown a subscrihers line-circuit and its con nccted apparatus, for a sub-station A, similar to that of A.

The operat on of my system will now be stated.

ssume that subscriber A desires to be connected to subscril' er .g. He first sets his sender l to the desired number. which we will assmne to be 3364. He then removes the receiver from the switch-hook. and we find the following circuit conditions: the talking circuit 50, 52, 53, broken at w by cam m circuit for line-relay M completed as follows: B, M, 5, n. n, 1, 55, 20 0 w. 10 56, 57, W W731. 5 3. 2 n". 77 ground and back to battery. It will be underst od that while l have shown the wheels W, as separate. each with its own pair of contact pens in series. both being closed when the wheels are set. this is for purposes of illustration only. For a number of four digits there should be four wheels, but there need be only one pair of pens. The four wheels can be set separatellf) Tel

ly, the teeth on each following the teeth on its next neighbor, and when running down they can and preferably will turn as one.

The current through the circuit traced lights the line-lamp m, by energizing the relay M. The operator, perceiving the signal, inserts the plug P, thereby putting battery on the sleeve side of line by the following path: B, 24, S, 14, 2 .2 p, 7", 4 (then through cutofi' relay N to ground and also), to 2, 10 w", 54, IV and ground. The cut-off relay having pulled up takes off the relay M and wire 5, as Well as the ground from contact a, and puts linewires 1 and 2 through 3 and 4 to the jack J. Current through magnet IV causes it to pull up its armatures w, one of which releases the wheel on and starts the wheels to, while the other permits the terminal spring of wire 58 to bridge across the wire 53. The train W runs down, sending the first number in a series of short breaks over the circuit B, 24, S, 14, 2 2 p, j, 4, n n 2, 53, 58, 57, 56, w, w, to, w, 55, 1, n, M, 3, p, 13, S and ground, whereby the relay S is caused to vibrate its armature, opening and closing a circuit which may be traced as follows: B, 24, s s, 240, s. 8 17, .2 2*, I, ground back to battery. Each short break puts battery onto this circuit, that is each short break in the line-circuit producing a corresponding make in the local circuit just traced, and causes the magnet Ito advance its indicator one step. The number of impulses in the first set determines the number to which the first indicator is stepped around.

At the same time that magnet I gets its first pulsation of current, the relay Z which is connected in parallel therewith through the wire 17 also takes current, and instantly pulls up its armature, which is made very sluggish in returning, so that on the succession of short breaks in the local circuit due to the short makes in the line, the armature will not fall back far enough to close the circuit of magnet Z. At the end of the first set of impulses, however, the first wheel V at the subscribers station produces a long make (or if the subscriber is manipulating the switchhook he lets it stay up for a moment). The effect of this is to cause relay S to hold up its armature and thereby cut off current from the relay Z long enough to permit the armature of the latter to fall all the way back and close the circuit 18 of the magnet Z as follows: B, 24, s s 19, 18, Z, ground. Magnet Z then pulls up and steps the side switch around, opening the springs .2 a and closing the pair 2, .2. The first break in the line of the second set, as the subscribers wheel W continues to run, produces a corresponding make in the circuit of magnet I, and of relay Z the second indicator disc thus being started and the circuit 18 being again broken. \Vhen this second set of breaks has been completed, a long make in the line again holds up the armature s and lets the armature of Z close the circuit 18 and step around the side switch, opening the contacts a, 2 and a The indicator magnets I, I are thus cut off entirely and the battery supply through the wire 14 is also cut off from line-wire 2 and the cut-01f relay N, the latter periniting its armature to fall back, and the magnet W losing current and permitting its armatures to fall back to open the circuit 53, 58. The line-lamp m may now glow, and if the subscriber is using his switch-hook for a sender he will hear the tone of generator G and the operator, perceiving the number which has been set up on the indicator by the magnets I, I, takes up the plug I and inserts it in the trunk jack J of a group bearing that number. There may be anywhere from 2 to 15 trunkjacks in a group, depending upon the percentage of lines which will be in use at once. In order to determine which of these are idle the operator may test them in the ordinary way, hence my reference to listening contacts in the key K. The test circuit is simple. It will be observed that the sleeve side of the trunk, 32, is normally to ground, but when a plug is inserted in any one of the trunk jacks the potential of the sleeve side is raised by the connection of the battery through the sleeve side of the cord.

As soon as the plug P is in the trunk jack the following circuit is established: B (in the cord), 24, S 16, 12, p. j, 32, 41, .2 2 35, P S and ground. The two relays l S thereupon pull up. The former closes the following circuit: B, 24, s", a 20, 19, 18, Z, ground. Magnet Z thereupon steps the cord side switch around one more step, closes the contacts 2 z, and also closes the contacts a and .2 The former closure puts battery back on the sleeve side of subscribers line, 2, again energizes magnet W, and lets the second pair of wheels W start. If the subscriber is manipulating his switch-hook he hears the generator G go off and the battery B come on. The relay S on the other hand, pulls up its two armatures, and closes the following two circuits: From battery B (in Figure 2), wire 40, s, s", 8 and if the relay S be deenergized, to s", magnet Z to ground; also from wire 31, 36, s 8 37, .2 2 39, S, and ground. Now, since the wire 21 in Fig. 1 has connected the point 8 t0 the tip conductor 11 of the cord, it is obvious that the breaks coming in over line 1 and causing the armature s of relay S to fall back, will produce a corresponding series of current pulsations over the following path: B (in Fig. 1), 24, s s, 240, 8, s 17, a", a 21, 11. At the point of connection with wire 11 the current divides, a portion going by each of the following paths: first, wire 15, relay S and wire to ground and back to battery; second, through conductor 11, to p, 7', 31, 36, s, 8 37, relay C and to ground; also 37, 2 2 39, and S to ground. None of these parallel paths will affect the others because they are directly to battery without any intervening resistance, but care should be taken that all the contacts and wire connections have a suflicient current carrying capacity to supply the three paths without burning out or undue heating.

Thus as the impulses come from the subscribers station due to the second pair of wheels, they are repeated by the relay S around the condenser G into the tip side of the trunk. These impulses coming over the wire 31 affect the magnet S, which is one of 'the two stepping magnets of the automatic switch P .As .it takes the impulses the wipers p are moved, vertically or in a rotary direction according to the type of switch, the vertical movement coming first if a Strowger switch be employed, and in either case the tens group of line-contacts J being selected in which the terminals of the wanted line are to be found. At the end of this set of impulses there comes a long make, as .before, whereupon the armature .9 remains back long enough to make contact with the point 8 and by energizing the magnet Z to step the side switch Z around one step, thereby opening the springs 2 2 and closing 2, 2, thereby putting wire 37 through wire 38 to the second magnet S of the switch P this being the magnet which in the Strowger switch moves the wipers around the row, to select the unit contacts wanted.

When the side switch in the trunk worked the last time, the switch Z of the cord also moved a step; but no effect was produced thereby, the contacts 2 2 being maintained closed during both steps. As the last or units impulses now come in as breaks over the line, they are repeated as before over wire 31, to energize magnet S, as stated. At the end of a set of impulses the long make comes, armature s in the cord stays up, and the relays Z and S of the side switches of the cord and trunk, fall all the way back, and both side switches are advanced a step. The switch Z does not open the contacts a", 2 until the switch Z makes its step to cut on 2 2 and 2 2 The switch Z opens the contacts 2 .2, thereby disconnecting the magnets S and S and closes the springs 2 2 thereby connecting the test relay Y to the wiper vp by the following path: Y, 43, 2 2 44, 34. As this wipe-r rests on the sleeve contact of the wanted line, if the sleeveside of that line has its .potential raised because of another connection existing, the magnet Y will instantly take current and will pull in its armatures thereby disconnecting the generator contacts 3 and 3 and bridging the busy-back G across the wires 31, 32 through the insulated contacts g, 1 3 y". The calling subscriber then hears the buzz of the busy-back, or if desired the voice of a phonograph saying Line is busy. The subscriber thereupon hangs up. A wire 47, it will be noted, connects as a branch of the wire 42 to the front contact 3/ of the relay Y. hen the relay Y pulls up therefore, it puts the release magnet X on the Wire 32 through the contact 3 and the magnet immediately takes current and pulls up. As 3 commonly used in automatic switches this what is called a two-step release, that is the magnet when it pulls up simply hooks its lever onto the release end of the detent pawls of the switch, and when it lets go the retractile spring of its armature is strong enough to pull off the pawls and so let the switch return to normal or inoperative position. Hence the switch remains set after the subscriber hangs up. When he hangs up, however, the operator perceives by the lighting of the supervisory lamp 8 that he has done so, and thereupon pulls the plug P out of the jack J. This cuts oil the current supply from the magnets S and X, and as the latter then lets go its armature, the switch is forthwith released. By Winding the magnet Y high and making it of considerable impedance, the amount of current abstracted from a busy circuit and the consequent annoyance to busy subscribers is no more than in any testing operation in systems now in use.

If the line wanted is not busy, the magnet Y gets no current when the switch wipers come to rest on the line terminals J, and the procedure is somewhat difi'e'rent. It should be stated here that after the last teeth of the set for number transmitting on the subscribers wheels W there are two or more teeth which are always operative for the purpose of setting the side switch Z". The side switch Z is unaffected after it makes the final movements stated, either because its arms have reached a stop which prevents further movement, or because the last steps go over tied contacts or solid contacts so as to maintain condi tions unchanged. The side switch Z has 5 movements, however, and if we cause the insertion of the plug P to give the first movement and cut in the magnet S simply by putting battery on at J and through the closure at s -s putting battery on Z before S is energized, which is the proper and economical course, still the subscriber only gives two long closures after that, by which means we are brought to testing, but the wanted line must still berung and the circuit then put through. So

two more invariable breaks of short duration are provided just before the W wheels run down. If the line wanted is not busy, the next break comes in, in due course, and the side switch Z makes another step, closing the generator contacts 2 and 2 which may be on one side as shown, or double-pole if desired. This puts generator to the wanted line. After any desired and predetermined interval the last break comes, followed by the final make as the cam 'w closes the talking circuit 505253, at the substation, and the switch Z makes its final step, opening the generator contacts, leaving the test contacts open, and taking spring 2 off spring .2 and putting it on 2", thereby cutting off the relay S and cutting on the release magnet X, which immediately pulls up and remains on the sleeve side of line during the conversation. Everything else is disconnected, however, including magnets S and S and wire 36. The same step of the side switch closes the contacts .2 z and z z whereby the trunk is prolonged to the Wipers, with the same clear talking circuit as in a manual trunking system, and with nomore contacts than any, but less than most, to talk through.

After the trunk is completed, the two supervisory relays S and S in the cord circuit are responsive to the two subscribers, as usual, and if the wanted subscriber does not answer within a reasonable time, the operator can ring him again by means of the key K, also as usual. This will not occur except in a small percentage of cases, and in fact automatic repeating of the ring can be arranged by merely giving the subscribers sender more ringing teeth and the switch Z" more steps or a set-back. If he finally fails to answer, the operator will withdraw the plug P and insert it in a busy back jack of usual pattern and connection, or can put the caller onto a manual or chiefs desk to be talked with and soothed if necessary. The subscribers operator under no circumstances attempts to talk, and in fact she cannot, having no equipment for that purpose, unless speed of service is to be sacrificed. She does not need to talk in the ordinary course of business, for if the steps in operation are followed carefully it will be observed that she gets signals for all that are perfectly plain. The line lamp lights when the man calls, and may also light after the first two numbers have come in, denoting that attention is required to insert the plug P. The supervisory lamps flash as the signals go through, and respond to all the movements of the subscribers afterward.

When the connection has been completed and the subscribers finish conversation, they hang up, and the supervisory lamps announce that they desire disconnection. The operator then pulls the plugs and the mechanism restores itself.

In case the calling subscriber desires a 're call he flashes his lamp, or if the wanted subscribers lamp continues to glow while the calling supervisory remains dark it may denote the same thing, although it is ditficult to distinguish this from the condition when the subscriber has not answered, and the operator then pulls the plug P, leaving the plug P in the jack. The indicator II and the side switch Z being at the same time restored to normal or Zero position, the operator pressing the button 1", the subscriber can get another number at once. He must set up his sender, of course, or manipulate his hook as before.

In the manner of showing the circuits in Figure 2, it is to be observed that the generator G and busy-back circuits are both tied onto one side of the trunk during conversation. It will be understood, of course, that double-pole cut-offs or switches are to be used throughout so these connections will not exist in practice, but are shown herein because of a desire to simplify the drawing as much as possible. Such connections would make the lines noisy.

In case the sender VVW be omitted and the switchhook be used in lieu thereof, all the circuits and apparatus of the sender would be eliminated, leaving the circuit that of any common battery telephone set, impulses going over the following path when sending: (see Figure 1): B, 24, S, 14, .2 2 p, j, 4, n n 2, 53, 52 (sender being omitted and the wires 58 and 52 tied together) T, R, H, 50, t, a, n 3, j, p, 13, S, and ground.

In practice the magnets Z and S may be solenoids or other sluggish magnets which close their local circuits only on a long break in the energizing circuits.

Having thus described my invention, what I claim and desire to secure by Letters Patent of the United States is:

1. In a telephone system, automatic switching apparatus, a controlling magnet therefor, auxiliary circuit changing apparatus, a controlling magnet therefor, a common control circuit, a connection from said circuit to the auxiliary magnet, and a connection also from said circuit through contacts in the auxiliary circuit changing apparatus to the switching magnet, each of said magnets being adjusted for a time constant such that one magnet will not respond to changes which will affect the other, substantially as described.

2. In a telephone exchange system, a two- Wire metallic line circuit with common battery at central, a sender having means to make and break a circuit, and an automatic switch having two-wire connections, con nective circuits, and an auxiliary or sideswitch, said side switch controlling the sequence of operating steps of said automatic switch and the connections of the operating parts of the connective circuits, and having a different time constant from the main switch, whereby the latter may be operated without operating the former, substantially as described.

3. In a telephone exchange system, a subscribers line terminating in a jack, an operators cord circuit terminating in plugs, a supervisory signal magnet connected with the line through said cord circuit, and an automatic switching apparatus operated by said supervisory magnet, substantially as described.

4. In a telephone exchange system, a subscribers line and substation, with means to make and break the line circuit controlled by the subscriber, a common battery for a plurality of lines at. the central office, connective circuits initially controlled by an ii operator, a supervisory signal magnet connected with the battery to the subscribers line through the initially established connective circuit, and an automatic switch responsive to makes and breaks as to its operating parts, in a circuit controlled by the supervisory magnet, substantially as described.

The telephone system comprising a common battery two-wire manual circuit with connecting cord having associated supervisory relays and lamps, control relays for the battery supply for said lamps, a two wire automatic trunk having a switch with controlling magnets adapted to be successively cut in for stepping to a desired line terminals, an auxiliary or side-switch tor the main switch having magnets with different time constants from those of the main switch and controlled through the same or associated circuits, and means at the subscribers stations to produce changes oi? different durations to control the respective switches, substantially as described.

(5. A telephone exchange system comprising line circuits, connective apparatus therefor arranged in successive links, one of said links comprising automatic connective means controlled by a calling subscriber, an operators signal receiving position and supervisory signals at said position adapted to indicate the progress and condition of a connection.

7. A telephone exchange system having combined manual and automatic connective apparatus at the central office, sending ap-' paratus at the subscribers stations, and means at the central office becoming effective when the manual apparatus has been actuated and the connection is initiated,

to inform the subscriber of the condition of the circuits.

8. In a telephone exchange system, subscribers lines, manual means for initiating connections therebetween, automatic apparatus thereby rendered available and placed under control of a calling subscriber, and signalling means simultaneously informing the subscriber of the condition of the circuits.

9. In a telephone exchange system, a plur'ality of line circuits to be interconnected, manually operated means for answering calls and initiating connections, automatic switches thereby brought under control of the calling subscribers, automatic signalling means to apprise a calling subscriber of the condition of the circuits, and supervisory signals associated with the manual connective means also under control of the calling subscriber.

10. In a telephone exchange system, subscribers line circuits, a central station, apparatus at said, station comprising both manually operated and automatic connective links, means for bring said automatic connective links under the control of the calling subscriber, and means for automatically apprising the subscriber of the condition of the circuits.

11. In a telephone exchange system, subscribers lines, a central station provided with apparatus comprising both manually operated and automatic connective links, means associated with said manually operated links for automatically indicating the group containing the desired automatic connective link, and means for placing the automatic connective link under the control of the calling subscriber.

12. In a telephone exchange system, a subscribers line and sub-station, means controlled by the subscriber to make and break the line circuit, a central station, automatic and manually operated connective links thereat, mechanism associated with said manually operated links to indicate the group containing the desired automatic connective link, said mechanism being responsive to the makes and breaks of the calling subscribers line circuit, and said automatic connective mechanism operating to effect a talking connection and being also controlled by subsequent makes and breaks in the subscribers line circuit.

13. In a telephone exchange system, a plurality of metallic line circuits, a number of automatic switches less than the number of lines for purposes of interconnection, auxiliary apparatus including means for signaling wanted subscribers associated with each switch, local or branch circuit connections for the auxiliary apparatus and for the switch, electromagnets controlling the switch in its movements, and the local circuits and auxiliary apparatus, said magnets having different time constants, means to connect a calling line to an idle switch, and means associated with a line when calling to produce current changes therein of different durations and according to a predetermined code, whereby such changes in the metallic circuit, without the use of grounds, may effect and control the switch movements and operate the auxiliary apparatus associated therewith, in proper order and sequence to select and call a wanted subscriber.

14. A telephone exchange system comprising a control circuit, associated automatic switch mechanismhaving waiting contacts divided into groups and a co-operating moving contact, a primary magnet and associated means for stepping said moving contact to a desired group of waiting contacts, a secondary magnet and associated means for stepping said moving contact to a desired contact in that group, quick and sluggish relays for controlling said magnets, means for energizing and deenergizing said relays by closing and opening said control circuit to operate said primary and secondary magnets to bring about the desired movements of said moving contact.

In testimony whereof I have afl'lxed my signature in presence of two witnesses.

EDWVARD E. CLEMENT \Vitnesses:

JAMES H. MARK, E. EDMONSTON, Jr.

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