US1218182A - Telephony. - Google Patents

Description

0.8. HULHSH.

TELEPHONY.

APPLICATION FILED MAY I31 l9l2- RENEWED AUG- L 1915.

N... NE E nil W NESSES D. S. HULFISH.

TELEPHONY.

APPLICATION FILED MAY 13, 1912. RENEWED AUG. 7, 1915.

Patented Mar. 6, 1917.

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D. S. HULFISH.

TELEPHONY.

APPLICATION FILED IIAY I3. 1912. RENEWEDYAUG. 7. I9I5.

Patented Mar. 6, 1917.

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TELEPHONY.

Patented Mar. 6, 1917.

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D. S. HULFISH.

APPLICATION r1120 an 13. 1912. RENEWED AUG. 1. 1915.

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TELEPHONY.

APPLICATION FILED MAY 13. I912- RENEWED AUG. 7.19.

Patented Mar. 6, 1917.

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TELEPHONY. APPLICATION HLED nu l3, m2. nsuzwm AUG. 1. I915. 1,218,182. q Patented Mar. 6, 1917.

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D. S. HULFISH.

TEEEPHONY.

' APPLICATION FILED MAY 13. m2. uznzwco AUG. 1.!915.

1 ,21 8, 1 82. Patented Mar. 6, 1917.

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D. S. HULHSH.

TELEPHONY. APPLICATION min IIAY 13. m2. awn/so we. 2.191s.

1,218,182. Patented Mar. 6, 1917.

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TELEPHONY.

APPLICATION HLED MAY 13, I912. RENEWED AUG. 7. l9l5.

Patented Mar. 6, 1917.

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D. S. HULFISH.

TELEPHONY.

APPLICATION HLED MAY13. 19x2. RENEWED AUG. 1. 1915.

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TELEPHONY.

APPLICATION FILED MAY 13. I912- IIENEWED AUG. 7. 1915. 1,218,182. Patented Mar. 6, 1917.

I3 SllETS-SHEET 13.

N\ Lu L nmw UNITED STATES PATENT OFFICE.

DAVID S. I-IULFISH, OF TORONTO, ONTARIQ, CANADA, ASSIGNOR TO CANADIAN INDE- PENDENT TELEPHONE COMPANY, LIMITED, 0F TORONTO, ONTARIO, CANADA, A

CORPORATION OF CANADA.

TELEPHONY.

Specification of Letters Patent.

Patented Mar. 6, 1917.

Application filed May 13, 1912, Serial No. 696,902. Renewed August 7, 1915. Serial No. 44,292.

To all whom it may concern:

Be it known that 1 DAVID S. llULrIsi-I, engineer, a citizen of the United States of America, residing at Toronto, in the county of York and Province of Ontario, Canada, have invented certain new and useful Im provements in Telephony, f which the fol lowing is a specification and a description of the manner and process of constructing and using the same, intended to be in such full, clear, concise, and exact terms as to enable any person skilled in the art to make and use the same.

My invention relates to telephone systems in general and to the application of methods and apparatus for telephone switching in central otticos of telephone exchanges. In some of its details, it is particularly adapted to systems of the Lorimer type of automatic telephone devices and I have shown it in this application, applied specifically to a system of circuits for the Lorimcr type of automatic apparatus with suggestions from time to time as to the general application of certain features of my invention to the general art of telephony in central oilices whether automatic or manual.

My invention. has for its objects the following:

(A) An improved system for indicating electrically the numbers for identifying a calling line, being a decimalindicator composed of a bank of relays.

(B) A method of calling among lines entering an automatic telephone exchange whereby the order of answering contemporancously existing calls may be varied from time to time.

(C) A combined sequence switch and division starter. v

(D) A system of test circuits tor determining the busy or idle condition of a tested circuit, wherclry the tested circuit may have either of two potentials impressed upon it during its busy condition and the testing circuits will reject it il it bears cithcr potmstirii.

llt) An improved oil-normal device in combination with a switch ha ving two- :novcmonts oi selection such that the offnormal device wiil show an oltnornml con- :litiou when the associated automatic switch is othnormal in either of its movements of selection the miitomatic switch being free to more in either movement from its position of rest.

(F) An improved system for testing a telephone line for busy or idle condition, and the subsequent adjustment of automatic switches in accordance with the result of the test,including a locking relay for recording the result of the transient test, the relay being held locked for a sufiicient time for reliable operation of the automatic switches requiring control subsequent to the test and dependently upon the test.

(G) An improved system of connnutators and associated circuits for ringing code ringing upon party lines in an ai'itoniatio telephone exchange.

(H) An improved system ot controlling circuits for an automatic telephone connective apparatus, controlled by the two telephones of the connection, and controlling the release of the connection at the will of either of the telephone users,

(K) A system of lamp signals for an automatic telephone exchange in which a different order of signals is produced when the line called for is busy as compared with the signals produced when the line called for is tested and found idle; also, an improved signal in a set of lamps whereby two lamps each having a definite meaning when burning alone, may be caused to burn simultaneously to express a third and independent meaning.

(M) An improved timer device or slow relay.

(N) An improved timer device having alarm points and automatic release points and adapted to close the alarm points first and to close the automatic release points after a delay subsequent to the closing of the alarm points whereby an abnormal action is at first indicated by an alarm and later is relieved automatically and the apparatus restored.

(l) An improved circuit and means in onnection with an automatic lamp alarm and release device whereby the atlomlant in charge of an automatic exchange may disable either the automatic release functions oi the telephone oliicc or the lamp alarm functions of the telepl'ione ollice, but not both.

(Q) An improved multiple brush for an automatic switch, engaging a plurality of contact points on the same level and closing through them a plurality of simultaneous circuits.

(h) A brush arrangement by which two independent multiple brushes act upon the same level of contact points and close simultaneous and independent circuits through the same level of points, each circuit being closed twice in a single cycle oi the switch, one closure for each multiple brush.

(SA) A system of mutual circuits between two automatic switches. such that the return oi either to normal will return the other to normal also.

(SB) A system of main circuits and of auxiliary circuits in an automatic exchange, such that the control ol an automatic switch normally by a line and its telephone is suh stituted by a central oliice auxiliary circuit in case the switch has no connected line.

(SC) A system of circuits by which the pilot switch when at normal restores other switches to normal, namely, the primary connector and the signal controller.

-(SD) A system of driving devices and circuits for a timing device whereby one timer may be driven at different speeds at different times.

(SE) I provide a division starter with a timing device whereby a second division will be started in case the first does not respond promptly.

(SF) A novel disabling circuit for a di vision starter when all divisions are busy.

(SG) A method of using duplicated devices or electrical circuits having a common destination by using them in order of rotation.

(SH) A method of using a group of electrical circuits having a common destination by dividing them into two small groups, one small group used in rotation and the remaining small group used as an overflow group and used in numerical order of precedence.

(SK) A system of circuits and apparatus for applying to the general practice of telephony the principles of selection of duplicated circuits last mentioned above.

(SM) A system and method of metering calls in which a call is recorded upon the meter of the calling line only as a result of the response of the called line.

(SN) A detail of metering system for general application in telephone exchanges by which certain lines may be designated as free service lines and calls terminating upon these lines will not register upon the meter of the callin line when the free service line respon 5.

(SP) The system for seizing a busy line with disregard of the guarding condition.

(SQ) An improved telephone for a sub scribers station suitable for a party line having features of reverting call ringing.

(SR) An llI'lPlOYWl party line telephone with an interference device.

In the drawings which accompany and form a part o'l this sywcification Figure 1 shows the circuits ol the primary connector or A-liue switch.

Fig. 2 shows the circuits of the pilot switch and. thousands or ringing register.

Fig. 3 shows the circuits of the relays, commutators, division timer and sundry other apparatus.

Fig. l shows the circuits oi the signal controller.

Fig. 5 shows the circuits oi the interconnector or trunk sclectm'. i

Fig. (3 shows the circuits oil the :accanulary ,-onnector, or l'l-line switch.

Fig. 7 shows the circuits of the line relays constituting the decimal iiulicator.

Fig. 8 shows the circuits of the decimal register controller.

Fig. 9 shows the circuits oi the division starter which is also the permutation con trollcr for the line relays or decimal indicater.

Fig. 10 shows the ci cuits of a telephone for a line having but one telephone.

Fig. 11 shows a simplified diagram of the circuits for conversation and for release under subscribers control.

Fig. 12 shows the circuits of the rota tional busy test.

Figs. 13, 14 and 15 show details of: Free meter lines.

Fig. 16 shows the circuits of a telephone for a party line.

Fig. 17 shows a party line telephone having interference features for party-line.

In the figures, numerals smaller than although sometimes used for identification, are not strictly reference labels within the ordinary meaning of the term; they are numerals indicating the order or relation of the parts adjacent to which they are found. or to which they directly pertain, as indicating the order of contact points in a row, or the order of rows in a contact bank; for example, the numerals l-to l l in Fig. 2 are stamped upon the apparatus as built and used and form a part of the apparatus illus trated by the drawing. Reference numerals 101 to 199 have been reserved for conductors, entering the pilot switch, 200 to 399 for apparatus parts, and 4:00 and higher for miscellaneous conductors. Like numerals refor to like parts throughout the many fig ures.

The switches.

The switches are of three types, called the cylinder type, the register type, and the co1nmutator type.

A switch of the cylinder type is illustrated in Fig. 4. The horizontal rows of small circles represent the fixed contact points projecting from the developed inner surface of an annular casting of insulating material; upon these contact points there move horizontally from left to right a set of brushes, shown in the figure as small fiat parallelograms resting upon the points of the first vertical set of points. A controlling magnet or clutch magnet 213 has an armature adapted to engage a notched disk to restrain the disk from turning. The disk is attached to the brushes of the cylinder switch. hen the clutch magnet is charged by current passing through it, its armature is withdrawn from the notched disk and the disk is permitted or caused to revolve in the direction shown by the arrow. carrying with it the brushes of the associated cylinder. The disk (and therefore the brushes of the switch) may stop only in positions corre sponding to notches in the periphery of the dish, and these notches therefore represent the only possible stop positionso'fthc brushes of the switch.

In the primary connector of Fig. l, the stop positions of the brushes are all but one in the first quadrant of revolution, as indicated by the location of eleven notches in the clutch disk.

In the pilot switch of Fig. 2 there are fourteen stop positions, irregularly distributed. The vertical sets of contacts of the cylinder are numbered horizontally l-to-M, the stop positions of the brushes are numbered in the line above, l-to-le't, each number appearing twice, over each of the two adjacent sets of points occupied by the main set of pilot brushes in each of the indicated stop positions, resting normally when not in use upon N0. 1 stop position, or contact sets 1 and 2. The horizontal rows of cylinder points are numbered 1-to-14 from top to bottom, at the left.

The pilot switch of Fig. 2 has also a set of auxiliary brushes, their pairs on 3rd, 7th and 9th levels, resting normally on points of 34th and 35th sets and moving with the main brushes. The main brushes of the 7th level are connected. by a wire to the auxiliary brushes of the same level.

In the signal transmitter controller of l ig. t, the clutch disk has four notches. The disk is geared to the brushes in the ratio of one revolution of the disk for two revolutions of the brushes. The complete cycle of operations of the switch is effected in two complete revolutions of. the brushes, or one revolution of the disk. The stop positions o l the brushes are: normal position on contact set No. 1, first stop position on contact set WU. i just before the end of the first revolution: second stop position on contact set No. 1; third stop position on contact set No. just before the end of the second rev olution.

The interconnector of Fig. 5 and the secondary connector of Fig. 6 are switches similar to that of Fig. 1. The division starter of Fig. 9 is a switch similar to that of Fig. 2 but with a dilierent distribution of stop notches, without a register, and with a single set of brushes.

In this specification, a contact point in a cylinder switch (or in a register bank) is identified by giving its vertical row counting from the left and its position in the row counting from the top; thus: 1X1 upper left point of any bank; pilot 23264, the pilot point, middle of bottom row of bank connected to conductor 105. When two points are engaged by two connected brushes, the points are indicated by a hyphen connection; thus, pilot points lXlEl-lQ, where the points are in the same vertical row, or pilot points 27X3-28X3, pilot points 39-7X7-7, where the engaged points are not in the same vertical row.

A switch of the register type is illustrated in Fig. l at the top. The arcs of small circles represent rows of fixed contact points. upon which move the brushes shown as small rectangles upon set No. 0 of the points. The brushes are carried by the ratchet, which is under spring tension against the pallet, and which is permitted to move step-bystep under control of the register magnet 214:- This register, complete, is carried by the mechanism. carrying the cylinderbrnshes, to which the register parts are wired. It is restored to normal position, after having been operated, by mechanical devices which restore it during the second quadrant of revolution of the clutch disk.

The ringing register of Fig. 2 is in fixed position, but is located adjacent to an associated cylinder switch, and is restored to normal by the return of the adjacent cylinder switch, such as the pilot switch of Fig. 2. The brushes of the register are reversed. moving from right to left.

The registers of Figs. 5 and 6 are similar to that of Fig. 1 and are similarly restored.

A switch of the commutator type is illustrated in Fig. 8, the decimal register controller. The developed. cmnmutator ring oi long segment Q32 and fifty smaller segments, with its associated brushes, comluctors, relay and clutch, form lhe decimal register controller as a whole, whose function it is to operate the decimal register of u started division to assist in the identification and seizure of the calling line.

The e is one decimal register controller for each switchboard section or group 0? divisions, one such controller thus serving all of a group of lines and controlling the derimul registers of all of the corresponding grpup of connective divisions.

The decimal register controller brushes are equipped with the direct-clutch, which starls its associated brushes when the clutch n'lagnet is charged and stops them when the clutch magnet is discharged and the dog of the clutch drops into the next notch ol the clutch dish. The disk has four notches, but as the two brushes are duplicates and the switch :u-eomplishes its electrical cycle in onehalt revolution, there result From the Tour notches but two stop positions with one brush upon the torty-sixth small segment, 230, and with the brush upon the li'ltieth or last small segment, the companion brush in each instance being upon the long segment, 232.

The switch of Fig. 9 is the division starter and line sequence controller. The pilot clutch magnets of the connective divisionr; when normal are charged only through this starter. The clutch magnet of the first connective division is shown at 215 in Fig. 2, being connected to wire 121. which is shown attached to cylinder point 3X6 in Fig. 9; the corresponding wire of a second division is shown attached to cylinder point 7X6 in Fig. 9. The division of Fig. 2 is further associatcd with Fig. 9 by the wire 128 shown attached to cylinder point 3X3 in Fig. 9; the corresponding wire of a second division is shown attached to cylinder point 7X3 in Fig. 9. These two wires, upon cylinder points 7X6 and 7X3 in Fig. 9 are illustrative of a second complete division such as shown in Figs. 1, 2, 4, 5, 6 and parts of Fig. 3. The starter is sole per group of divisions (say six to twelve) and per associated group of lines (say one hundred).

The single-Zinc telephone.

The automatic substation telephone com prises the usual items of a telephone set, and in addition an automatic call sender. The circuits for a single-station-line telephone are shown in Fig. 10.

Grounded brushes, 240, of which four are shown, are adjustable by moving projecting buttons by the telephone user according to indicators to place ground upon one pin in each segment (about a quadrant, as drawn) of a circle of pins 241, which contains several such segments and upon which a conducting arm 242, rides.

The means for propelling the arm 242 over its circle of pins comprises a main spring, a crank for Winding the main spring, and an electric escapement controlled by the magnet 248. The escapement permits the arm to move in steps, forty-three steps being required to complete one revolution. The electric escapement is ineffective to make the first step, the first step being made mechanically, preferably by the crank which winds up the main s ring, the electric escapement then being e ective when properly controlled to make the remaining forty-two steps.

The devices of the central ollice are adapted to send forty-two impulses tor the control ol' the call sender escapelnent, Forty-one from the signal controller and one l'rom commie tutor No. 8.

To set the signal transmitter to eil'ect conncction with a. desired teleplume sul'istation, the indicator buttons are set to the directory number of that substation by n'ioving the buttons independently to positions in which they will indicate the said directory number. The wires from the first two indicator points of each set to the contact pins in the circle engaged by the arm 242 are shown in the diagram, Fig. 10. The remaining points are connected in corresponding manner, except the last or tenth point, (directory nuurlier 9,) which is left unconnected. Core tact arm 242 normally engages the point 24;) and thus normally holds the talking bridge subject to control by the hook switch 246. Connection from the first conductor of the line 421, to the arm 242 is made throilgh a brush connection. When the arm is moved forward mechanically one step by the operation of starting a call, it engages a contact pin 244 which connected directly to earth or through a return wire to minus battery.

A switch, 247, composed of a pair of contact springs, is adapted, when closed, to complete the circuit for the stepping magnet 249 from the second conductor of the line 422, to earth. The springs of the switch 247 normally are disengaged from each other but are forced into engagement by means of a cam lever 249 moved by a. cam disk 239 secured to the shaft of the contact arm 242.

A notch in the cam disk 239 permits the springs of the switch 247 to move the arm 249 and to disengage themselves when the arm 242 stands in the normal position, or in connection with pin 243. When the arm 242 is moved from its normal position, by the action of starting the call, the cam disk 239 operates the lever 249 to close the switch 247, the disk 239 then preserving the closed condition of the switch 247 until the arm 242 completes its revolution and resumes its engagement with the pin 243.

The lines entering a central oliice are dividedinto groups of, say, one hundred lines per group, and the automatic equipment of the central office is for the most part divided also, each group of apparatus serving a group of telephone lines; such a group of apparatus is called a switchboard section, or simply, a section.

In each such section the switches for the most part are grouped into groups called connective divisions, each group or division constituting a connective unit analogous to a switching cord pair equipment in a manual telephone switchboard,

The automatic switches which make up a connective unit or connective division in the figures of this application are: primary connector or A-line switch, Fig. 1; pilot switch and thousands or ringing register, Fig. 2; (relays, timer, lamps, condensers, resistances, Fig. 3;) signal controller, Fig. 4; inter-connector, Fig. 5; secondary connector or Bdine switch, Fig. 6.

The automatic switches of a section, common to all divisions, aredecimal register controller, Fig. 8; division starter, Fig. 9.

The total process of connecting two lines automatically in such an oiiice comprises: (1) A primary adjustment by which a connective division is associated with a calling line. (2) Selective adjustments by which circuit-selecting switches are adjusted to select such circuits as will result ultimately in associating the connective division with the line desired by the calling line and indi cated by the preliminary manual adjustment of its call sender. Test and preliniinary ring by which the line selected is rung upon it not found engaged. (4) Repeated ring until the call is answered. (5) Maintenance of a condition for conversation after the ring is answered and release by subscribers control. (6) Restoration automatically of all parts of the connective division after conversation and release. (7) Throughout all of these operations the connective division is supervised by a system of lamp signals which operate to announce normal action and abnormal action, if any. (8) The division is further guarded by antomatically operative restoring or normaling circuits and devices which act to restore it to normal condition for further service in event of an abnormal operation. (9) Special service requirements compel some specialization of apparatus or circuits, or both.

A) Early forms of decimal indicators, constructed for one hundred lines, have comprised a rotating device capable of being stopped in one hundred different positions, each position corresponding to a line served by the device. \Vhen thus stopped by a calling line. the decimal indicator identified the calling line by placing an electrical potential upon two identified and line-identifying wires in two sets, each set comprising ten wires and one Wire being identified in each set. These sets were the decimal set and the unit sct. By the wire identified in the decimal rich the tens digit oi the calling line was made known and by the wire identified in the units set, thc units digit of the calling line was uncle known. My improved deciinal indicator comprises one hundred line signal or line-indicating relays, each relay having two pairs of contact points, one pair being connected properly to place an identifying clcctriral potential upon the proper wire in the tens set corresponding to the line of that relay and the other pair of contact points being similarly connected to place an identifying potential upon the proper wire in the units set. The charging of the line relay thus identifies the calling line by identifying two conductors which in turn identify the line, the subsequent selection of the line being accomplished by the division upon fundamental principles heretofore used. Associated with each line signal relay is a line cut-off relay and associated with each units wire is an additional signal relay, making a bank of two hundred ten relaysin all required for a completely equipped decimal indicator for one hundred lines. My improved relay dcrinnil indicator otters instantaneous response to a calling line, thus eliminating the period of time required for the rotating device to engage the calling line and my improved relay device obviates cer tain adjustments which were involved in the rotating device.

(B) In the rotating decimal indicator the calling lines were served on either of two principles of selection, dependent upon the circuits used. The first principle was that the lines should be served in rotation as they might call, the search being made in numerical order and each calling line being assigned to a connective division before the rotating decimal indicator proceeded further in its search, the rotating; device being held motionless upon a calling line so long as all connective divisions were engaged. The second plan was that lines should be served as in the first plan until all connec tive divisions became engaged, after which the rotating device would not stop upon any calling line unless a connective division were idle and in condition to serve the line. The second plan therefore left to a matter of chance the selection of one calling line from several calling lines, when, all connective divisions having been busy, one connective division was released and made available for serving one of the several calling lines. In my improved decimal indicator, the lines are arranged in a series circuit in an order whereby certain lines have prccwlence over all others and are served in precedence when the connective divisions are insufl'icicnt to serve all calling lines. To provide against immoderate use of the coi'inective divisions by certain favored lines to the exclusion of lines loss favorably located upon the scrirs circuit. l provide a pcrnnitution device which from time to time changes the ordrr ol precedence of the lines and thereby distributes the service of a group of connective v divisions more uniformly among the lines served by that group.

(C) l accomplish the periuuting requireincnts of my improved dci-innil indicator by utilizing the cylinder switch ol the division lib lllO

starter and in the drawings which acconr puny this s wcification. 1 show the lowest six levels of the division starter cylinder thus utilized.

(1) The full economy ol a trunk circuit, having a minimum number of comluetors. in an automatic telephone exchange, can he realized at times only by using some One conductor for more than one function in the progress of setting up, maintaining and disrupting a. connection. I have met a. requirement of this nature by using the same c,on ductor for the operation of the clutch of a distant switch and for a busy test coiuluctor offering a CUJItlltlUll suitable for electrical test, to determine whether a distant switch is in normal position or otherwise. As the conductor thus used will vary its potential from time to time as operating currents do or do not pass over it to control the distant switch, it is necessary for the testing circuit at any moment to show that the distant switch is engaged, regardless of the variations of potential upon the conductor serving the double purpose of switch control and busy test. I have provided three different potentials in the automatic central oflice of which two may be applied to the conductor in question for such switch control, the third being applied for test purposes, the testand-control conductor being so associated with apparatus that it will be entirely open only when the distant switch is idle so that no current will flow from the testing devices to the wire in question if the switch be idle but current will flow from the test devices to either of the two operatin potentials if the switch be busy. By the ow of current from the test device, it may be known that the distant switch is busy and the test device may be controlled in accordance therewith.

(F) In the automatic telephone system shown in the accoi'npa-nying drawings it is necessary to adjust the selecting switches to variant positions according as the selected line is found to test engaged or free. If the tested line he found engaged, the pilot switch is advanced immediately after the test but if the tested line he found free, the si nal controller is advanced immediately aer the test and the pilot switch is advanced subsequently.

To provide ample time for moving these switches to their positions of adjustment in accordance with the result of the test upon the selected line, I provide a locking test relay which by locking will record the result of the test indefinitely or for such a length of time as may be required for the adjustment of the selective switches involved.

To insure the maintenance of the locking circuit for a sufficient time to move the pilot switch, I carry the locking circuit through the pilot switch, and the locked relay.

(G) In my improved system of commututors for ringing in code manner upon party lines, I provide commutators which produce a group of impulses arranged in a code manner, and 1 cause these eommutatm's to rcpea; each group of impulses as frequently as is possible. in order that the code ring upon a telephone line may be re pcated less 'lrcrpiently than my rapidly revolving connnutators, I provide an. auxiliary con'nnulator. My auxiliary commutator is so designed and so connected in the circuits of the ringing devices that it permits the operation from time to time of one group of the code in'ipulses, withholding the operation of the intervening repetitions of the group. i do this by connecting in series in a single circuit the fast and the slow eonnnutators, and so associating the eonnnutators that the slow commutator will be closed during one cycle of the fast commutator and be open for a predetermined number of succeeding cycles.

I provide also in the pilot switch two ringing positions. In. the first rii'iging position, the fast commutators are effective to ring at all times; and I provide means for pern'iitting the pilot switch to remain in this position during one and one only cycle of the fast cumn'iut-ators, thus attaining a single initial code ring, with a minimum of delay before. the first ring.

(H) In my improved system of controlling circuits I provide four stop positions for the pilot switch in which the further nioven'ient of the pilot switch, and therefore the entire command of the connection, is under control of either of the two connected telephones. In the first position, pilot stop No. 9, the lifting of either telephone from the hook will advance the pilot. The next position, pilot stop No. 10, is held when the A-linc telephone is off the hook and the Il-line telephone is on the hook. The third position, pilot stop No. 11, is held when the A-line telephone is on the hook and the B- line telephone is off the hook. The fourth position, pilot stop No. 12, is held by both telephones off the hook and the pilot switch is advanced by-hanging up either telephone. Advantages are obtained by the control of visual signals indicating the condition of the connection, and advantages are found in the complete system of control by which connection at all times is under complete control 'by either telephone without any operations other than the usual hook switch operations common in either illltOll'lfit-lC or manual telephone usage.

(K) In association with a connective division, I provide a set of signal lamps and a system of lamp signals by which the condition of the connective division may be known. These lamps are mounted promi' nently upon the frames supporting the switches and in such manner that an attendant seated in a supervising position may see from the one view point all the lamps of a central office or of his portion of a central oflice. In connection with this plan, my system of lamp signals is such that the attend-ant. by watching the lamp signals may know to a very considerable degree the progress made by any call which is received by the central oiiice apparatus. I provide three lamps, and a normal call normally handled by the central oiiice apparatus will produce illuminations of these lamps, or two of them, in a predetermined order and of predetermined duration which may he recognized visually by the attendant as indicating a (J()llfl(u1ti\'0 division and a telephone user both acting in a normal manner.

While a call terminating upon a line previously engaged (the call therefore being defeated because of the guard or busy test upon the called line) may be considered in some ways as a normal call, I provide such details in my system of lamp signals and circuits that the sequence of signals produced when calling an engaged line is different from the sequence of signals produced when calling an idle line. By this detail of improvement, an attendant watching the lamps of a distant operating division, may know whether the call is terminated upon an idle or a busy selected line.

I provide also a. signal which is displayed when the subscriber upon the B-line of the connection lifts his receiver before the lifting of the receiver upon the A-line. This is a condition having a peculiar interest in an automatic exchange of the character herein described. My improved signal for this condition also has a peculiar interest; in that for the display of this signal I cause to glow simultaneously two lamps, neither of which indicates when glowing alone any part of the condition indicated when both glow simultnncously.

, Two lamps are provided to indicate normal operation of switches and the third lamp provided as an alarm lamp indicating an abnormal delay in the operation of the switches whether upon the part oi. cen tral ollice devices or uphn the part of the telephone users.

(M) For the detection oi automatic switches operating abnormally, a timing de vice which is the equivalent of a slowly acting relay may he used, the device being so adjusted that it will become operative as soon as an automatic switch becomes operathe and that it will become inoperative whcu thiautomatic switch reaches its nor mal position or any predetermined position. The relay contacts may be connected in an alarm circuit or in a circuit to restore the antomatic switch to normal. The speed of operation of the slow relay or timing device then may be adjusted to give the automatic switch a suiiicient interval to operate in normal manner before the timing device closes its contact points. By means of such a device, an automatic switch may be brought to the attention of an attendant by means of the alarm when the switch is not operating in normal manner or at normal speed; or, on the other hand, an automatic switch may be caused always to return to normal in readiness for further service, in case it has not operated in normal manner and at normal speed.

(N) I also combine in one device the functions of an alarm timer and a release timer.

I provide in my improved timer, two pairs of electrical contact springs, and I prmide a moving striker driven step by step toward. the springs. I so place the springs with reference to the striker that the striker engages and closes the first pair of springs upon a predetermined step and I so place the second pair of springs that upon the next succeeding or some predetermined succeeding step, the striker will engage and close second pair of springs either directly or by moving the first pair of springs or contact members to engage the second pair.

I thus cause my improved timer to close two circuits, each having a predetermined delay after the beginning of operation of the timer, one circuit having a greater delay than the other if desired. It is obvious that both circuits may be closed simultaneously if desired as an alternative method of operation.

By means of the delay of the second closing after the first, I am enabled to connect my timer contact points, so that an abnormal action of an automatic switch is first indicated by an alarm and later is relieved automatically by restoration of the switch, or I may provide an automatic release and cause an alarm later it the automatic release is not efieetive.

(l When an automatic exr.:hange is fully supervised, as in the busy hours of the day, it may he desired that every case of abnornial action be studied by the attendant and that no automatic releasing be permitted, all abnormal switches being released and restored manually by the attendant; in such a case it is desirable that the automatic release circuits of the timers be disabled. When the automatic exchange is unattended as at night and on holidays, the alarm circuits associated with autmnatic releasing dcvices have no practical mine and may be disabled, leaving the normaling ol' the auto matic switches wholly to the care of the timer-controllcd releasing circuits. It is obvious, however, that the exchange should not be left at any time without either alarm or release circuits operative.

I provide in connection with my improved

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