US256432A - Telephone-exchange system - Google Patents

Description

(No Mbdel.) 4 Sheets-Sheet 1A 1-1, T. GREENPIELD. TELEPHONE EXCHANGE SYSTEM- No. 256,432. 7 Paten ted Apr. 11,1882.-

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( No Model.) 4 Sheets-Sheet 2.

E. T. GRB ENFIELD. v TELEPHONE EXCHANGE SYSTEM.

110.256.4552. Patented Apr. 11,1882.

227, Lav 026751:

(No Model.) 4Sheets-Sheet3.

E. T. GRE-ENPIELD.

I TELEPHONE EXCHANGE SYSTEM. No; 256,432. Patented Apr. 11, 1882.

Wi nesses.-

" g 1 nvenT02' UNITED STATES PATENT OFFICE,

EDWIN T. GREENFIELD, OF BROOKLYN, N. Y., ASSIGNOR OF ONE-HALF TO THE HOLMES BURGLAR ALARM TELEGRAPH COMPANY, OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

SPECIFICATION forming part of Iietters Patent No. 256,432, dated April 11, 1852.

Application filed April 23, 1880. (No model.)

To all whom it may concern:

Be it known that I, EDWIN T. GR-EENFIELD, of the city of Brooklyn and State of New York, have invented a new and useful Improvement in Telephone-Exchange Systems and Apparatus therefor, of which the following is a specification.

The present invention relates to the construction and arrangement of apparatus to be used in a central telephone-office, whereby exchanges between the various customers and offices connected with such central office can be ett'ected quickly, easily, and economically; and the principal features of the invention are the use of a switch-board provided with a local ground, the combination, with. a switchboard, of multiple receiving and transmitting instruments, and a series of automatic drops or equivalent signal devices arranged in combination with the switch-board and the listening-oft' apparatus, all as more fully herein after set forth and claimed.

In the accompanying drawings, which fully illustrate this invention, Figure l is a general 2 5 perspective view of the combined apparatus,

S B indicating the switch-board, it the multiple receiver, T the multiple transmitter, and L O the listening-oft mechanism, consisting ofa series of automatic drops, a key-board, and an 0 ordinary telephone. The switch-board, vfor convenience of illustration,is shown of smaller size relatively to the other parts than would occur in actual use. For the same reason the transmitter, the receiver, and the listening-oft apparatus are shown in closer proximity to the switch-board and to each otherthan would be found convenient for practical purposes.

Fig. 2 is a rear View of the switch-board, showing the switches and the wires of the 10- 0 cal ground, as well as the general wiring of the board.

Figs. 3 and 4 are side elevations of one of the switches, Fig. 4 showing the position of the parts with the switch-plug P in place, and

7 5 Fig. 3 the parts with the plug removed.

Fig. 5 is a sectional view of the compound receiver, showing two of the magnets, Fig. 6 being a plan of the same receiver with the cap and diaphragm removed.

Fig. 7 is a perspective of the compound transmitter, the hinged door or cover which carries the mouth-piece, the diaphragm and. the connected parts being thrown open and a portion of the case being broken away, so as: to show the interior of the instrument.

Fig. 8 is a longitudinal section through the key-board and one of the drops, showing also the connection of these parts with the switchboard and with the earth.

These drawings represent the improved ap- 6o paratus as arranged for use in connection with the service-lines of eight subscribers or enstomers; but the system may be applied to any desired number of lines.

'Referring to the several divisions of the apparatus more in detail, the receiving-instrument R, to which all the service-lines pass. after leaving the switch-board, is a multipleinstrument constructed on the general plan illustrated in Figs. 5 and 6, in which there is 79 shown a single diaphragm combined with a multiplicity of magnets and coils, the number of coils being one-half the number of lines in the system. To efiect this the lines are connected with the instrument in pairs, each pair of conductors beingjoined to a common coil. So far as concerns this multiple receiver, the present invention relates to the coupling of two conductors upon a single coil or spool, the use generally of a multiplicity of magnets or 80 of coils in a single receiving-instrument being the special subject of another application for patent, heretofore filed by me, and therefore not claimed herein. As fully explained in such prior application, the use in asingle receiver 8 5.

of a number of separate magnetsror coils, orequivalent devices, enables a single listeneron to keep watch over aud'reeeive orders from a large number of lines. The transmitter T is also a multiple or compound instrument, containing a single mouthpiece and diaphragm and one-half as manyinduction-eoils as there are customers in the system, the secondary wires of the several coils uniting the service-wires in pairs inlike man- 5 ner as they are united in pairs by the coils of the receiver. The mouth-piece and diaphragm, and the parts more immediatelyconnected therewith, may be of any ordinary construction, and therefore are not here shown in i detail. So far, again, as concerns this multi-l ple transmitter, the present invention relates only to the coupling of two conductors upon a single induction-coil, the use generally in a transmitter of a multiplicity of inductioncoils or equivalent devices under the control of a common diaphragm being the special subject of another application, filed by me contemporaneously herewith, and therefore not claimed herein.

The switch;board S B consists in partof an upright frame provided with the usual metallic union'strips, A B O D, arranged horizontally upon its face, and with vertical metallic strips upon its rear, the latter being so arranged relatively to holes passing through the former and through the board that metallic plugs inserted in such holes will bear against the elastic flanges ot' the vertical strips and thus enable the operator at pleasure to establish electrical connection between any one of the front and any one of the rear set of strips.

E is the main wire of a local ground-connection, leaving the switch-board at any convenient point, as F, and grounded at G. From this main wire E branch wires are run to each of the switches S S S 810. The switches are each composed of three projecting lips or flanges, l I l", of elastic sheet-brass or other equivalent material, so arranged that the insertion ot' a metallic pin or plug of the proper size through any of the lower series of holes in the switch-board will press the lip Z away from the lip I, as shown in Fig. 4, while the withdrawal of the plug will permit such lip to spring back into contact with Z, as shown in Fig. 3. Moreover, the lip Z is so related to the lip I that after the switch-plug is inserted between them, as above indicated, it bears against them both, and thus establishes an electrical connection between them, such connection in turn being broken when the plug is withdrawn.

. The customers lines are represented by 1,2, 3,4,5,6,7,and S, and the wiring of the'switchboard is as follows: From the several binding-posts through which these lines enter the switch-board the wires pass to the corresponding vertical strips, 1 2 3, 850., and thence to the upper member, I, of the switches. From the lower member, 1, of the switches the wires 1" 2 3 &c.,run toasecond set of binding-posts, and after leaving these last named posts the wires are looped together in pairs-1 with 2, 3 with 4, &c.-each-loop being passed through the transmitter and the receiver.

From the above explanation of the construction of the apparatus its operation will be apparent. Vhen the switch-plugs are all in place in the switches S S, &c., each customers line is in connection, through the switchboard, with both the receiver and the transmitter, and through these with the ground of that line to which it is itself coupled. It follows that any customer can at any time call the central station by simply throwing his telephone into circuit with his special line in the usual way, and, also, that when he has thus put himself in communication with the central station he can hear any message that may be spoken into the multiple transmitter, whether intended specially for him or for anyother person. It, now, any customer, as No. 3, desires to communicate with any other, as No. 6, he calls the central otfice and gives his order, as 3 on 6. The switchman receiving the order from the listener-on disconnects No. 3 from No. 4 and No. 6 from No. 5 by removing the plugs from the switches S and S of lines 3 and 6, and inserts these plugs directly above in any one of the horizontal union-strips, as B, which may happen at the time to be unoccupied. In this way the lines of No. 3 and No. 6 are connected, each taking the ground of the other, and No. 6 being rung up, everything is in condition for the transaction of business between them. Although by this arrangement No. 4 has been out off from the ground of No. 3, and in like manner No. 5 from the ground of No. 6, yet the closing of the lips l l of the switches of lines 3 and 6 consequent upon this withdrawal of the switch-plugs has thrown lines 4 and 5 onto the local ground E, and as these lines still pass through the transmitter and the receiver communications can take place freely over these lines to and from the central ofiice.

The great advantage of thus coupling up the lines in pairs, which seems to be rendered practicable only by the use of the local ground, is that the multiple instruments-the receiver and transmitter-can be made more compact than would otherwise be possible, and thus a larger number of lines be brought under the control of a single operator or set of operators.

The mode of ringing up the customers when two are to be connected for purposes of communication is as follows: After the two are plugged in on one of the horizontal unionstrips, as above explained, such strip is tapped several times with the key K. This key forms one pole of a local battery, and each time it touches the strip a current dividing at the point of contact passes over each of the two customers wires and rings abell, or otherwise sounds an alarm,in the otfice of each customer. This is notice to the calling customer that he is connected with the person desired, and is ,notice to the called customer that he is connected with some one who desires communication with him, and thereupon the called customer throws his telephone into the line and hails such other person. Manifestly, also, instead of using a battery with which to excite the lines for signaling the customers, an induced current might be similarly utilized by means of a key, K.

The listening-off apparatus is constructed and operates as follows: Each of the horizontal union-strips A B O D of the switch-board is electrically connected with a corresponding key, A B, &c., upon the key-board by wires arranged in any suitable manner. The contact-points of these several keys, when the keys are depressed, touch a metal strip, H,

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the switch board.

which is connected through the binding-post I with the earth, and at any convenient point in this earth-connection there is placed an ordinary transmitting and receiving instrument, J. From the wires that connect the unionstrips of the switch-board with the several keys of the key-board branch wires diverge and pass to corresponding drops, A B, &c., which are placed convenient to the keyboard, and from these drops other wires lead down to the earthconnection of the key-board. In'practiee there should be as many drops as there are unionstrips on the switch-board; but in the drawings, Fig. 1, only two drops are shown, one of which, D, has its cover up, indicating that the corresponding stripis not in use, whilethc other, B, has its cover down, displaying the letter B,which indicates to the listener-oft that two customers are plugged onto the corresponding strip.

L'L is an electro-magnet having an armature, M, mounted upon or forming one end of a pivoted lever, the other end of which is notched to hold uprthe cover of the drop, which is readily accomplished so long as the armature is out of contact with the magnet.

The moment a cur-rent passes through the coil and magnetizes the soft-iron core the armature is drawn down, and this elevates the notched end of the arm attire-lever and releases the cover, which immediately falls and displays a number or a letter like that which distinguishes the corresponding union-strip of Each branch wire which leads oft from the connections between the switch-board and the key-board connects with one end of the coil of the electro-magnet of the corresponding drop, the other end of this coil being connected with the metallic frame of the drop, and thus when the cover of the drop is raised an electrical connection is secured, through such cover and the spring a, against which the cover bears when raised, with the wire that leads from the drop to the earth-connection of thekey-board, such wire being insulated from the frame of the drop; but when the cover of the drop falls the contact between it and the spring a is broken and the elect-rical connection through the drop is'destroyed.

From this construction it follows that whenever two service-lincs are plugged onto one of the union-strips of the switchboard, and a local current is thrown onto such strip for signaling the two customers, as above described, a portion of such current will also flow to the drop, and by exciting the electro-magnet will throw down the cover of the drop, and thusindicate to the listener-oft that the correspon ing strip isin use. Thereafter it becomes the duty of the listener-off to keep watch of the lines connected with the union-strip indicated by the drop and ascertain when communication between these lines has ceased, whereupon he is tonotify the switchman, who will at once disconnect the two lines and restore each to its normal connection with the switchare passing between thelines which are shown by the drop to be jacked together upon any one of the union-strips is to depress the key corresponding to such drop, which at once puts the telephone of the listener-off into a branch circuit dtverging from the main circuit between the two customers who are electrically connected. By simply listeningin his telephone the listener-off can ascertain whether communications between the customers have ceased. Thus one listener-off can readily keep watch over a large number of lines.

It will be seen thatthe above system in its practical working is one of great simplicity and efficiency. Three persons, at the central office can readily take charge of a large number of lines and transact the business with accuracy and without confusion. All the words that it is necessary to have spoken at the central office are the repeating to the switchman by the listener-on of the order which he hears in his receiver-as 3 on 6--and the order from the listener-off to the switchman to disconnect any parties who have ceased talking, such order, for instance, being, in brief, disconnectB, which signifies disconnecttheparties who are jacked onto union-strip B. Thus all confusion at the central office, with the consequent danger of mistakes, is avoided. There is practically no chance of any custoniers who have ceased communication being cut off from the central office, as sometimes occurs under some of the existing systems and three attendants in the central office can serveefliciently at least six times as many customers as would be practicable under one of the most generally adopted systems in use at the present time.

I do not in this application claim the abovedescribed mode of ringing up and signaling customers by the use of a local battery, having withdrawn my claim therefor, as originally filed, for the purpose of making the subject thereof the basis of an application for a sepa* rate patent.

What is claimed as new is- 1. The combination,in a telephone-exchange system, of a plurality of service lincs with multiple receiving and transmitting instru ments at the central station, each line being connected through the instrument with another line of the system, whereby each line normally or in a state of rest is grounded through such other line.

2. The combination, in a telephone-exchange system, of a pl nrality of service-lines arranged in gronps,.so that in their normal condition or a state of rest each has as its ground the'ground IIO of some one of the other lines, a switch-board, and a local ground at the central station, arranged substantially as set forth, whereby any line out oif from its normal ground may take the local ground of the central station.

3. The combination,in a telephone-exchange apparatus, of a switch-board, a multiple receiver, and a plurality of service-lines leading through the switch-board to such receiver.

4. The combiuation,in a telephone-exchange apparatus, of a switch-board, a multiple transmitter, and a plurality of service-lines leading from such transmitter to the switch-board, and thence to the customers.

5. The combination,in a telephone-exchange system, of two service-lines and a single coil in each of the instruments (the receiver and the transmitter) of the central station, each line being connected through such coils with the otherline,whereby each line normally orin a state ofrest is grounded through the other line.

6. In combination with the key-board of the listening-01f apparatus, a series of automatic drops arranged and connected to be operated at the time of placing, the customers in communication, substantially as described.

7. In combination with the union-strips of the switchboard of a central telephone-station, a series of automatic drops arranged to be operated by the same current with which the switchman signals the customers, substantially as set forth.

EDWIN T. GREENFIELD.

Witnesses:

H. F. NEWBURY, J AS. ToRNNEY.

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