US2071053A - Inter-outer telephone system - Google Patents

Description

Feb. 16, 1937. R. VARLEY I 2,071,053

INTER-OUTER TELEPHONE SYSTEM Filed July 5, 1954 5 Sheets-Sheet 1 WITNESS.

Feb. 16, 1937. R. VARLEY INTER-OUTER TELEPHONE SYSTEM Filed July 5, 1934 3 Sheets-Sheet 2 INVENTOR WITNESS.

Feb. 16, 1937. R VARLEY 2,071,053

INTER-OUTER TELEPHONE SYSTEM Filed July 5, '1954 3 Sheets-Sheet 3 E a/Z INVENTOR WITNESS.

o wmmkx Patented Feb. 16, 1937 UNITED STATES PATENT OFFICE Inter-Outer Telephone Corporation,

Dover,

Del, a corporation of Delaware Application July 5, 1934, Serial No. 733,824

41 Claims. (Cl. 179-1) This invention relates to improvements in telephone systems, and more particularly to an interouter telephone system.

One of the objects of the invention resides in acoustically coupling the transmitter of a hand set phone of a public, battery telephone system with a receiver of a one-way or a two-way private battery telephone circuit and simultaneously acoustically coupling the receiver of the same hand-set phone with a microphone or a transmitter of another one-way private telephone circuit which includes one or more electronic amplifiers, without disturbing the leased property of the public telephone system.

16 Another feature of the invention is to fully utilize the economic advantages of electronic amplifiers in the pick up and transmission of sound from the receiver, and transmitter of a public telephone instrument, thereby broadening go the use of the regular telephone system. It provides a service for the regular system not now inherent therein, in that direct telephonic communication may be so amplified in transmission to and from the telephone instruments that not 5 only is it possible to converse between stations without holding the-receiver-transmitter instrument to the ear and mouth, but unrestricted conversation between groups or among several people at one station may be carried on with 30 one or more persons at another station or stations without the necessity of using individual telephone instruments. Further, it is possible to link in (non-electrically) auxiliary telephones or systems such as inter-phones, not part of the regular 35 telephone system, with the full range of service available in the regularsystem.

The majority of subscribers of telephone systems are now the users of the hand-set type of telephone instrument commonly known as the 40 French type, and the use of this particular type of phone lends added advantage to my system, as it facilitates the handling of the same to and from its normal supporting stand, and

Figure 3 is a wiring diagram of the system shown in Figure 1.

Figureiisawiringdiagramofthe formofthe invention shown in Figm'e 2. V

Figure 5 is a vertical sectional view of the inter- 5 mittently operated signal bell.

Figure 6 is a top plan view of the electronic amplifier at the office station showing the phone rest in normal position in full lines, and in operative position in dotted lines. 10

Figure 7 is a top plan view of a modified switch control device.

Figure 8 is a side elevational view of the device shown in Figure '7. r

Figure 9 is a detail vertical-sectional view through the electric signalling device.

Figure 10 is a diagrammatic view showing my inter-outeroflice telephone system associated with a standard installed inter-oifice system.

Figure 11 is a top plan view of the electronic 2o amplifier and phone rest used in the system shown in Figure 10.

Referring to the drawings by reference characters, the letter A designates an oflice station outfit and B an extension station thereof, while C designates a public telephone subscriber's receiving and transmitting appliance of the French type which is arranged in a two-way battery telephone system, a lead from which is shown at D. The telephone appliance C includes the usual cradle stand E and the hand receiving and transmitting instrument F provided with a hand grip H, an ear receiver R at one end of the hand grip, and a mouth transmitter T at the opposite end.

constituting part of the oflice station A is a box-like casing In which houses an adjustable electronic sound amplifier ll of the conventional construction employing vacuum tubes of the amplifying and rectifying type, choke coils, trans- 40 formers, condensers, and all other elements which are commonly used in the construction of such devices. For example, an amplifier such as RCA Victor portable sound amplifier, type PG-63, and Universal amplifier assembly (6 5 watt) may be used. Other types of announcing outfits maybe used in the system about to be described but it is not believed necessary to specifically describe the same, hence I have illustrated the electronic sound amplifier diagram- 5 matically, furthermore I do not require more than two stages of amplification.

Referring particularly to Fig. 3 of the drawings, rotatably mounted in the casing or cabinet II is a vertical shaft I2, the upper end of which extends through the top of the casing and carries a phone instrument rest |3 which includes a pair of diametrically spaced upstanding fingers |4|4 (Figs. 3 and 6). The inner end of the shaft |2 carries a sleeve I5 of di-electric material on which is mounted arcuate contacts l6 and I1 having vertical extension portions I8 and I9 respectively. Fixedly supported adjacent the contact IS in the path of turning movement of the extension portion 3 thereof are fixed spring contacts 20 and 2|, while disposed in electrical engagement with the contact l6 proper is a fixed spring contact 22. A fixed spring contact 23 is in constant engagement with the contact I! while spaced opposite spring contacts 24 and 25 are fixedly disposed in the path of the extension portion IQ of the said contact IT. The phone instrument support constitutes a switch for the selective opening and closing of the several electric circuits hereinafter described and is manipulated by the actuation of a handle or knob 26 (Fig. 1) fixed to the shaft I2 and extending through'a slot in the front wall of the casing l0.

Mounted in the top wall of the casing It at one side of the phone rest I3 is a microphone 21 while mounted diametrically opposite the microphone 21 is a receiver or sound reproducer 28.

The microphone and receiver are provided with annular receptacles 2| and 28 of insulating material which are so spaced that the ear piece or receiver R and the mouthpiece or transmitter T of the hand-set phone instrument F may rest therein and overlie the microphone 21 and receiver 28 respectively when the instrument F is in a position upon the rest l3 and the rest has been turned to the desired selective position to effect an acoustical connection therebetween. A grill opening 29 (Fig. 1) is provided in the front wall of the casing adjacent the microphone 21 and is within the range of sound spoken into the opening. It being understood that the receiver R, receives the messages coming in over the wires of the public telephone company and transmits sound messages to the microphone of the announcing outfit which includes one or more electronic amplifiers and which comprises a oneway private telephone circuit, the speaker of which is located at any distant place.

The electronic amplifier receives its current from a source of A. C. and is shown connected to an outlet wall socket 43, a portion of the power circuit being shown at 3| (Fig. 3) and in which the fixed contacts 20, 2|, and 22 are arranged. In Figure 3 of the drawings; the phone rest I3 is shown in a neutral position but it will be apparent that a turning movement of the same in either direction will cause the power circuit 3| to be closed through one or the other of spring contacts 20 and 2| to pass current to the electronic amplifier The microphone 21 is arranged in a two-wire, one-way operatively independent receiving circuit 32 which is operatively coupled up with the electronic amplifier and also arranged in said circuit is a loud speaker 33 at the extension station B.

The amplifier includes a volume control rheostat knob 92 as shown in Figures 1 and 2 for manual operation by an operator at the ofiice station to regulate the intensity of the amplifier and control the volume of sound produced by the receiver or loud speaker at the extension station B.

Also located at the extension station B is a cabinet or casing 34 'with which an ear phone 35 is associated. Normally, the ear phone 35 is hung upon a pivoted hook end of a lever 36 which extends from one end 01' the casing, the other end of the lever extending within the casing and acting as a switch actuating member for a spring switch member 31 which is arranged in the circuit 32. Normally. the lever 36 holdsthe spring contact member 31 in engagement with a fixed contact 38 also arranged in the circuit 32. In order that electrical waves transmitted through the circuit 32 may be received at the extension station through the ear phone 35 instead of the speaker 33, there is provided a fixed contact 39 in the path of movement of the spring contact 31 upon its release by the lever 36, and the same is arranged in a branch circuit 4|! of the circuit 32.

The earphone 35 is arranged in the branch cir-- cuit 40 whereby removal of the ear phone from the hook lever 36, will cause the breaking of the circuit 32 through the loud speaker 33 by reason of the release of the spring contact member 37, and the engagement of contact 31 with contact 39 whereupon the electrical waves through the circuit 32 may be received as audible speech upon the ear phone 35.

For the transmission of sound or speech from the extension station B to the ofiice station A, or to the transmitter T of the instrument F when placed upon the rest |3, I employ within the casing 34 an adjustable electronic amplifier 4| which is similar to the amplifier hereinbefore described. The electronic amplifier 4| receives its current through a power circuit 42 from a source of supply such as a wall socket 43 and which is controlled by a manual switch 44 arranged in the circuit 42. Operatively connected with the electronic amplifier 4| is a microphone or transmitter 45 which is arranged in a twowire one-way operatively independent transmission circuit 48 and is operatively associated with the amplifier 4| when the power circuit 42 is closed. One wire of the circuit '46 leads to the spring contact 23 while the other wire thereof leads direct to the receiver 28. The contact 24 is also arranged in the circuit 46 and is connected to the receiver by a wire 41. Thus it will be seen that by turning on the switch 44, the circuit 46 is rendered operative to transmit electrical waves, responsive to speech thereover.

Under normal conditions when the interoflice system is not in use, the switch associated with the rest l3 occupies a neutral position in which the stationary spring contacts 23 and 25 are in engagement with the parts l1 and I9 respectively of the rotatable contact. I By reason thereof, the speaker 48 is connected into the transmitting circuit 46 through the wires 49 and 50. Thus the party at the extension station, by closing the power switch 44, may speak to the operator at the main station through the speaker 48.

By providing a receiving circuit and a transmitting circuit which are operatively independent of each other, it is possible to employ a different source of energy in each circuit and individually control the intensity of the energy in the respective circuits to suit operating conditions. Also, the complete isolation of the circuits and the in struments arranged therein avoids possibility of feed back in the circuits. Feed back is also avoided by the use of the French phone instrument in whichthe receiver and transmitter are fixed relative to each other thus preventing direct impingement of sound from the receiver on the diaphragm of the transmitter.

Assume that a call is received at the oflice station A over the public telephone system, and it is desired to acoustically couple up the French phone F with the interofiice system to permit a person at the extension station B to receive the message and converse with the party calling through the public telephone system. The operator at the office station A lifts the instrument F from the cradle E and before placing the instrument F upon the cradle I3 to acoustically couple the instrument with the inter-oflice system, the operator at the station A communicates with the party at the station B. This may be accomplished by the operator at the office station A by actuating the handle 26 of the main control switch to the right to cause the closing of the power circuit 3| through the fixed contacts and 22 and the movable unitary contact Iii-l8, whereupon the amplifier II is energized and the receiving circuit 32 is rendered operative. During movement of the phone rest l3 to the right to close the circuit 3|, the movable contact 19 has been moved but maintains its engagement with the contact 25, thus maintaining the transmission circuit 46 for operation through the loud I speaker 48.

The operator at the oflice station speaks through the microphone 21 and by means of the loud speaker 33, is able to call the proper party to the receiver at the extension station B. The party at the station B proceeds to close the switch 44, thus closing the power circuit 42 to the amplifier 4| whereby the transmission circuit 46 is rendered operable. The party at station B may now speak through the microphone 45 and the speech.will be transmitted as electrical waves through the circuit 46 to the loud speaker 48, whereby the operator at station A may be notified that the required party is ready at station B to receive the message from the phone of the public telephone system. Having thus established twoway communication between the operator's station and the extension station, the operator is ready to effect the acoustical coupling between the inter-oilice system and the public telephone system. However, before doing so, it is necessary to move the phone rest I 3 and associated switch into its extreme opposite operating position, so as to render the receiver operative and eliminate the loud speaker 48 from the circuit.

By reference to Figure 6 of thedrawings, it will be seen that normally, the pins l4--l4 of the instrument rest I3' are in alinement with the microphone 21 and receiver 28, whereupon they prevent the placing of the French phone in position to aline the mouthpiece T with the microphone 21 and the ear piece R with the receiver 28. Thus the main control switch must be rotated from neutral position to move the pins -44 to a position out of alinement with the micro phone 21 and the receiver 28, such as the dotted line position shown in Figure 6, and at which time the control switch is in an on position for acoustical coupling with the public telephone in-' stnnnent.

After having called the party at station B intended to receive the message;'the actuating lever 26 and associated switch is moved to the left through the neutral position and into its other operating position, as shown in Fig. 6', to cause the contact 24 to engage the extension contact I5, and the spring contact 25'to disengage con-.

tact I3, so that the transmission circuit 46 in- /contact with the bell 55.

cludes the receiver 28 instead of the loud speaker 48.

The operator then places the public telephone instrument F in position upon the rest l3, as J indicated in Fig. 6, whereby the acoustical coupling between the interofiice and the public telephone systems is established. Of course, the position of the receiver R and transmitter T in the pocketed annular receptacles 21 and 28*, pmvents the switch from being again rotated until the telephone instrument F has been removed and the acoustical coupling broken.

When an acoustical coupling has been made between the instrument F and the microphone 21 and receiver 28, the sound from the receiver R is picked up by the microphone 21 and the electrical waves thus set up are amplified by the electronic amplifier ll, whereupon they pass through the circuit 32 to the loud speaker 33.

In the event that the party receiving the message at the extension station B prefers to use the ear phone 35, the same may be removed from the hook 36, thus disconnecting the circuit 32 through the loud speaker 33 and coupling up the branch circuit 40 through the contact members 3'! and 39 with the receiving circuit 32. The party at station B may talk into the microphone 4.5 and the electrical waves set up by the voice are amplified by the electronic amplifier 4| from which they pass through the circuit 46 to the transmitting instrument or reproducer 28 over which the mouthpiece of the phone F is positioned. After the party at the extension station B has completed his conversation, the switch 44 is turned ofi.

In order that the operator at the office station A may be warned thatthe main switch through the power circuit 3| is still on, I provide an audible signalling device 5| which is arranged in the circuit 3| and is operated Whenever the switch is in an operating position. The working mechanism of the signalling device 5| is quite similar to the mechanism used in A. C. operated clocks and includes a self starting induction motor 52 (Fig. 5) preferably of the'synchronous type and which is arranged in parallel with the two wires of the power circuit 3|. The motor 52 operates a cam-53 which intermittently operates a pivoted hammer 54, the cam teeth 53 tending to. move the hammer away from a bell 55 while a spring 56 returns the hammer'54 into striking By varying the cam teeth 53 of the cam 53, the bell may be operated once a minute, every half minute or other various time intervals.

' After the-party at the extension station B has completed his conversation with the outside telephone system, the operator at station A, by listening at the receiver 28, may learn that the conversation has ceased and then lifts the instrument F from the rest l3, and replaces it upon the cradle stand E after which the manipulating handle 26 is moved to actuate the rest l3 and associated switch to neutral position to open the power circuit 3|. This not only renders the amplifier ll inoperative, but leaves the speaker 48 connected into circuit, and therefore in readiness for another call from the extension station.

As previously mentioned, inter-oflice communication is carried on between stations .A and B, with the switch in its right hand position, before acoustically coupling the telephone instrument F with the inter-office system with the switch in its left hand position when a call is to be transferred to a party at station B, but such inter-ofllce communication may be carried on at any time by the operation of the central switch 26 into its right hand position, in the manner hereinbefore mentioned.

In Figures 2 and 4 of the drawings, I have illustrated a slight modification of my invention wherein the various circuits and parts are the same as that shown in Figures 1 and 3 with the exception of the transmission circuit from the extension station B to the receivers at station A.

The transmission circuit from station B to station A is designated by 46' and includes a microphone 45 mounted in the cabinet 34. Instead of receiving its current from the source shown in Figures 1 and 3, the transmission circuit 46' includes a battery 43 and a rheostat 51 for varying the resistance in the circuit and correspondingly varying the intensity of the electrical waves transmitted through the circuit, or, the transmission circuit 46' may include a dry rectifier of the copper-oxide type now in commen use for low voltage devices. A push button switch 44' is also arranged in the circuit and both the switch and control knob of the rheostat 57 are disposed exteriorly of the cabinet 34 within reach of the user of the head phone 35. Thus it will be seen that after the party at station B has been called to the receiver at said station he proceeds to press the push button switch 44' to close the circuit 46' and continues to hold the switch on until the end of the conversation. Of course, other types of switches may be used. The intensity of the electrical waves over the circuit 46 may be selectively controlled by the adjustment of the rheostat 51 and the sound reproduced by the loud speaker 33 and receiver 35 arranged in the amplifier circuit controlled by the rheostat knob 92 of the amplifier ll.

In order that, the operator at the oflice station A may be notified as to when the circuit 46' is rendered inoperative or open by the release of the push button switch 44 at the end of the conversation, and at which time the telephone instrument F should be lifted from the rest l3 and returned to its cradle stand E, I provide an electric buzzer 58 arranged within the cabinet I!) at the office station A. One of the coils 58 of the electro-magnet of the buzzer is arrangedin the battery operated transmission circuit 46' while the other coil 58* thereof is in parallel with the power circuit 3 I. When the transmission circuit is closed and in operation, the electro-magnet 58 is energized by the battery 43' and the buzzer armature is held against vibratory movements, irrespective of whether the electro-magnet 58 is energized from the main source of A. C. power. With the circuit connected to the power line only, the buzzer will operate and constitutes an audible signal to the operator at the oflice station A that the party at station B has released the push button switch 44' which is the equivalent of having hung up. Then to stop the operation of the buzzer, the power switch must be turned by the operator to its neutral position which is done as soon asthe French phone is lifted from its rest 13. Obviously the French phone will then be replaced in its cradle of the public telephone system.

In Figures 7, 8 and 9 I have illustrated a modification which may be used, more particularly in association with the transmission and receiving circuits of my inter-office system hereinafter described in connection with Fig. 10, and the same consists of a combined phone rest, acoustical coupling and audible signalling device. The electronic amplifier cabinet is shown at I6 while mounted on the top thereof is a telephone base 58 containing the usual dial mechanism embodied in a French style telephone. It is also provided with the usual cradle 6| upon which the French type instrument 62 rests. When at rest upon the cradle, the ear piece or receiver 63 overlies a microphone associated with a receptacle 64 mounted in the coupling device and operatively connected to the circuit 32, whereas the mouthpiece or transmitter 65 overlies a receiver or sound reproducer provided with a receptacle 66.

Mounted horizontally on the cabinet I is a turnable snap switch 61 having a manipulating fiat knob 68 provided with concavities 69 in opposite ends. The switch 61 is conventional in construction and is provided with an on or closed position and an off" or open position and takes the place of the main control switch which is operable by the phone rest l3 of Figure 1, and a detailed description of the same is not believed necessary. By turning the knob 68 of a. clockwise turning switch, a quarter turn, to the right from its normal off position as shown, the switch is merely brought into position to connect the amplifier to the source of power. The knob 68 of this clock-wise turning switch is so made as to prevent it from being turned to the left, in accordance with well known practice.

For the purpose of lifting the telephone instrument 62 a sufficient distance 'to effect an acoustical coupling between the phone 62 and the inside system, I pivot a bell crank lever at the rear of the top of the switch cabinet. The free end of the horizontal arm ll of the bell crank terminates in a fork 12 which underlies the phone 62 beyond opposite ends of the cradle 6|. A roller 13 is journaled in bearings extending from the underside of the arm H and is normally disposed in axial alinement with the switch 61 and in the path of movement of the concave ends of the knob 68. When the knob is turned a quarter turn to the right, the roller rides over the curved surfaces 74 and seats in a concavity 69, thus lifting the arm ll upwardly, which raises the phone 62 off its cradle 6|. This upward movement of the arm 1| causes the shorter downwardly extending arm '15 to move inwardly for a purpose now to be explained.

Mounted upon the top of the cabinet ill at the rear of the switch cabinet is an electric clock 16. The shaft of the clock motor, which constitutes the second hand shaft, is designated 11 and mounted thereon is a cam 18 having any desired number of cam teeth 19 extending radially therefrom, two of which have been shown at diametrically opposite points. Pivotally mounted within the clock casing 86 is a bell crank lever 8|, one arm 82 of which depends downwardly and terminates in an angular head 83 which extends through an opening 84 in the casing 80 and is disposed in the path of a roller 85 mounted on the free end of the arm of the bell crank 76. The other arm of the bell crank 8| terminates in a downwardly extending finger 86 which is normally out of the path of the cam teeth 79 by reason of the bearing engagement of the roller 85 with the head 83 of the arm 82 which is held inwardly at an angle to the vertical as shown in Figure 8. However, when the roller 85 moves away from the head 83, the arm 82 drops to a vertical position by gravity and the finger 86 moves into the path ofthe cam teeth 19. A spring bell clapper 81 is mounted on top of the horizontal arm of the bell crank 8| and upon each engagement and release of the finger 86 by the cam teeth 19, the clapper will strike a bell 88 mounted within the casing 88. If the shaft 11 makes one revolution each minute; the bell 88 will be struck every half minute.

When the telephone conversation has been terminated, the operator turns the'snap switch knob 68 another quarter turn to the right, whereby the energizing circuit of the amplifier is opencircuited and the power is out 01f of the amplifier.

By this construction, an acoustical connection between a subscribers public telephone and an inter-omce system may be effected withouttouching the telephone instrument, other than at'the time of first receiving an incoming call. Obviously, if upon picking up the telephone instrument in answer to an outside call, it is learned that some party at one of the branch stations is wanted, the switch knob 68 is turned by the operator to mechanically raise the supporting forks l2 and also to energize the amplifier, before the instrument is replaced upon the supporting fork 12 in acoustical relation to the interofiice system. The actuation of the switch knob 68 controls the lifting of the telephone instrument from its cradle and its replacement thereon, and also controls the operation of the audible signal just described.

In Figure 10 I have illustrated my system of telephone communication in association with one of the present type inter-oifice communication systems which includes a main ofiice phone G operatively connected with similar outer ofiice extension phones M, whereby inter-ofiice conversation may be carried on between the main phone G and any of the extension phones M, or between any of the extension phones M. This type of system provides push button call means for calling any selected station, and permits of selective talking. v

Located at the main office is the acoustical coupling and electronic amplifier outfit I hereinbefore described together with the public telephone equipment C. The receiving circuit 32 and transmission circuit 46 are the same as hereinbefore described but the receiving and transmitting instruments at the extension stations, as shown in Figures 1 to 4, are dispensed with, and in their stead is a series of French type phones J, respectively provided at the extension phone stations M. These phones J are of the type in which each is provided with a push switch button K in the handle portion and may be hung upon a hook. The cord L containing four wires connects the ear piece and the mouthpiece of the phone with the set of wires 32 and 46 whereby grasping of the phone J and depressing the switch K will operatively connect the said phone in the circuits 32 and 46. Thus a person at the extension; stations may converse through the circuits 32 and 46 with a party calling from the public telephone system through the telephone equipment C, the phone F thereof being acoustically coupled with the microphone and sound reproducer located beneath the receptacles 2'! and 28 respectively. By the arrangement just described, the operator at the main office station G may receive a call through the phone F and transfer the same to a party at any of the extension stations M. The party at the extension station is called to any of the phones by the operator at the main station ringing the desired phone M and calling the proper party to the phone and advising him of the call, or a code signal may be used, that is any particular number of rings on a phone M is an indication to answer the phone J at that particular station.

In the apparatus shown in Figs. and 11, I have illustrated a double push button switch 88 of a well known type which is mounted in the top of the cabinet of the electronic amplifier III. The switch 89 includes an "on push button 8| which is in alinement with the microphone and sound reproducer receptacles 21 and 28' so as to be depressed by the handle of the phone when placed in position to eflect an acoustical connection. A push button 9] constitutes the "oil" button and is manually pushed by the main office operator only after the acoustical coupling has been broken to shut on the inter-ofilce system. The switch 89 is connected in the amplifier power circuit and has an on and an "off" position. It takes the place of the main control switch shown in Figures 1 to 4 which is operated by the turning of the phone rest IS.

The modification shown and described in connection with Figs. 7, 8, and 9 is particularly adapted for use in the system of Fig. 10, in which it is intended to be used in the place of the public telephone set EF and the acoustical coupling and amplifier outfit l0.

Throughout the specification and claims the term receiving circuit is employed to denote the inter-ofiice telephone circuit through which the party at a branch station receives the messages emanating from the receiver of the public telephone instrument which are picked up acoustically by the transmitter or microphone of the inter-office system at the operator's station and are relayed to the receiver or reproducer of the branch station.

The terms transmitting circuit or transmission circuit are used to designate the interoifice telephone circuit through which the party at the branch station speaks and by means of.which his messages delivered into the transmitter or microphone at the branch station are transmitted to the receiver or reproducer at the operators station from which they are picked up acoustically by the transmitter of the public telephone instrument and thence are delivered over the public telephone system to the desired party.

While I have shown and described several embodiments of my invention, I wish it to be understood that various other arrangements and constructions may be resorted to if desired without in any way departing from the spirit of my invention, and I do not restrict myself to anything less than the scope of the appended claims.

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

1. In a system of telephonic communication, the combination of a public telephone system having a subscribers receiving and transmitting instrument, and an electrically independent inter-ofiice system including two operatively independent two-wire one-way telephone circuits acoustically coupled with said receiving and transmitting instrument for receiving and transmitting telephone messages from and to said public telephone system, one of the two-wire one-way telephone circuits including an electronic amplifier.

2. In combination with the telephone receiving and transmitting instrument of a subscribers public telephone, an inter-ofiice telephone system including a main office station and an extension station, a microphone and a sound reproducer located at said main omce station, a sound reproducer and microphone located at said extension station, a two wire receiving circuit connecting said first mentioned microphone with arranged, switch means for controlling each of said circuits and located at the respective stations, and means for acoustically coupling said telephone instrument with the microphone and sound reproducer at said main office station.

3. In combination with the telephone receiving and transmitting instrument of a subscribers public telephone, an inter-office telephone system including a main otfice station and an extension station, a microphone and a sound reproducer located at said main office station, a sound reproducer and microphone located at said extension station, a two wire receiving circuit connecting said first mentioned microphone with said last mentioned sound reproducer, a two wire transmission circuit operatively independent of said receiving circuit and in which the microphone at the extension station and the sound reproducer at said main ofiice station are arranged, switch means for controlling each of said circuits and located at the respective stations, signal means located at the main office station operable upon the closing of said receiving circuit by the turning on of its switch means to indicate to the operator at the subscribers main station that the switch in the receiving circuit is at the on position, and means for acoustically coupling said telephone instrument with the microphone and sound reproducer at said main ofiice station.

4. In combination with the telephone receiving and transmitting instrument of a subscribers public telephone, an inter-ofiice telephone system including a main ofiice station and an extension station, a microphone and a sound reproducer located at said main station, a sound reproducer and microphone located at said extension station, a two wire receiving circuit connecting said first mentioned microphone with said last mentioned sound reproducer, a two-wire transmission circuit operatively independent of said receiving circuit and in which the microphone at the extension station and the sound reproducer at said main oflice station are arranged, switch means ior controlling each of said circuits and located at the respective stations, signalmeans located at said main office station and normally inoperative but operable upon the on position of the switch means in said receiving circuit and inoperable upon the closing of the switch means of said transmission circuit whereby the operator at the main station may be notified as to when said transmission circuit is open or closed.

5. In combination, an inter-ofiice telephone system having a main oflice station, a public telephone instrument of the French type located at said'main oflice station, said inter-oflice telephone system including a receiving circuit, a transmitting circuit operatively independent of said receiving circuit, a microphone and a sound reproducer in said receiving and transmitting circuits respectively and located at said main oilice station and in fixed spaced relation, and means 6. A system of telephonic communication comprising in combination, a French type telephone instrument of a public telephone system wherein the transmitter and receiver are respectively disposed at opposite ends of a. hand grip member,

an interphone system including two operativelyindependent two-wire one-way circuits, an electrically operated announcing outfit arranged in one of said two-wire one-way circuits, said announcing outfit having one or more electronic amplifier tubes and a microphone, a sound reproducer arranged in the other of said two twowire one-way circuits and disposed adjacent said microphone, and means for supporting said telephone instrument with its receiver and transmitter in intimate relation to the sound reproducer and microphone respectively to provide an acoustical coupling therebetween.

7. A system of telephonic communication comprising in combination, a French type telephone instrument of a public telephone system wherein the transmitter and receiver are respectively disposed at opposite ends of a hand grip member, an interphone system including a receiving twowire one-way circuit and an operatively independent transmitting two-wire one-way circuit, an electrically operated announcing outfit arranged in each of the two-wire one-way circuits, each announcing outfit having one or more electronic amplifier tubes, and a microphone, a sound reproducer arranged in each of the two-wire oneway circuits, the sound reproducer in said transmitting circuit and the microphone in said receiving circuit being arranged adjacent each other, and means for supporting said telephone instrument with its receiver adjacent the microphone of said receiving circuit and its transmitter adjacent the reproducer of said transmitting circuit to effect an acoustical coupling therebetween.

8. In combination, a public telephone system having a subscribers receiving and transmitting telephone instrument, an electrically independent interofiice transmitting and receiving telephone system, switch means for rendering said interofiice telephone system operative and inoperative, signal means arranged in said interoflice telephone system and operable when the switch strument and said inter-oflice telephone system.

means is in on position, and means for acoustically coupling said subscribers receiving and transmitting instrument with said interofiice telephone system when said switch means is in on position and for preventing operation 01' said switch means to off position until such time as the acoustical connection is broken.

9. In combination, a public telephone system said independent telephonesystem to said public system. I

10. In combination, a public telephone system having a subscribers receiving and transmitting telephone instrument, an electricallyindependent interoflice telephone system including a transmitting circuit and a receiving circuit, means for acoustically coupling said interomce system with said telephone instrument, electronic amplifying means 'in said receiving circuit for increasing the intensity of the electric waves passing through said receiving circuit, a loud speaker and a hand type receiver arranged to be connected in said receiving circuit, and switch means arranged-in said receiving circuit for selectively opening and closing the receiving circuit to either said loud speaker or hand type receiver.

11. In combination, a public telephone system having a subscribers receiving and transmitting telephone instrument, an electrically independent interofiice telephone system including a twowire, one-way receiving circuit and a two-wire, one-way transmitting circuit operatively independent of said receiving circuit, a main oflice station at which the subscribers telephone is located and one or more extension stations, electronic amplifying means arranged in said re--.

ceiving circuit, one or more telephone instruments at the extension station or stations operatively connected to the two, two-wire, one-way circuits, and means located at the main office sta-' is acoustically connected with said interoflice telephone system.

13. In combination with the French hand type telephone instrument of a public telephone system, an interofiice telephone system, switch means for rendering said interofi'ice telephone system operative and inoperative, means for acoustically coupling said telephone instrument with said interoflice telephone system, means preventing operation of said switch means to inoperative position when said telephone instrument is acoustically connected with said interoffice telephone system, and audible signal means located adja:-

cent said telephone instrument and arranged in said interoflice telephone system and operable only when said interofiice system is in operation.

14. In combination with a French type telephone instrument and a cradle supporting stand therefor, an' interoflice telephone system-including a, receiver and a transmitter withinthe range of said telephone instrument when manually lifted free of and from its position ,of rest upon said cradle stand, switch means for rendering said interoifice telephone system operative and inoperative, means apart from said cradle supporting stand and mechanically associated with said switch means for supporting said-telephone instrument in-acoustical relation with said receiver and transmitter after the same has been lifted free of and away from its position of rest on said cradle stand sad when said switch means is in operative position.

15. In combination with a French type telephone instrument and a cradle supportingktand there1'or,-an interofllce telephone system including a receiver and a transmitter within the range of said telephoneinstmment when lifted from its position of rest upon said cradle stand, switch means .i'or rendering said interoilice telephone system operative and inoperative, means for supporting said telephone instrument in acousticalrelation with said receiver and transmitter after the same has been lifted from its position of rest on said cradle. stand and when said switch means association with the French type telephone instrument of a publictelephone system including a two-wire one-way receiving circuit, a two-wire one-way transmitting circuit operatively independent of said receiving circuit, an electronic amplifier arranged in said receiving circuit, and means for acoustically connecting said receiving circuit and said transmitting circuit with a French type telephone instrument.

17. A system of telephonic communication comprising in combination a public system station having a receiver and a transmitter, an interoflice telephone system including a local staiion having a receiver and transmitter respectively connected into independently operable transmitting and receiving circuits of said inter-office system, means for acoustically coupling said public receiver with said local transmitter and said local receiver with said public transmitter, and means for preventing feed back from said local station into the public system.

18. In combination, a public telephone system having a subscribers receiving and transmitting telephone instrument, an inter-oilice system including a receiving telephone circuit, a transmitting telephone circuit, -means for acoustically coupling said subscribers receiving and transmitting telephone instrument with the receiving and transmitting circuits, switch means located adjacent the subscribers telephone instrument and operable for rendering said receiving circuit operative upon the effecting of an acoustical connection, and for rendering said receiving circuit inoperative upon the breaking of an acoustical connection, and signal means located adjacent said telephone instrument and arranged in said receiving circuit and operable when said switch means is in operative position.

19. In combination, a public telephone system having a subscriber's receiving and transmitting telephone instrument, an electrically independent inter-oflice telephone'system including a transmitting circuit, a receiving circuit operatively independent of said transmitting circuit, each of the circuits having a source of electrical energy different from the other, means for acoustically coupling the subscribers telephone instrument with said transmitting and receiving circuits, and manual control means arranged in the respective circuits for regulating the intensity of the electric. waves passing through the respective circuits.

20. A system of telephonic communication comprising in combination a. main station, a

branch station, a public telephone instrument located at said main station, an inter-oflice telephone system including a receiver and a transmitter located at said main station, a transmitter and receiver at said branch station, a receiving circuit connecting the transmitter of said main station with the receiver at said branch station, a transmitting circuit separate from and independent of said receiving circuit and connecting the receiver at said main station with the transmitter at said branch station, each of the circuits having a source of electric energy difl'erent from the other, means associated with the respective circuits for selectively regulating the intensity of the electric waves passing through the respective circuits, the said means associated with the receiving circuit being located at the main station under the manual control of the operator at said station, and means located at the main station under the control of the operator of said station for acoustically coupling the public telephone instrument with the main ofiice receiver and transmitter of the inter-oflice system.

21. A system of telephonic communication comprising in combination, a main station, a branch station, a public telephone system having a telephone instrument located at said main station, an inter-office system having independently operable receiving and transmitting circuits connecting said main station and said branch station, means for acoustically coupling said public telephone instrument with said inter-ofiice system at the main station, means for building up weak audible sounds originating in the public telephone system and received by said public telephone instrument, and means located at the main oilice station under the control of an operator at said main station for controlling the volume of sound built up by said last mentioned means.

22. In combination, an inter-ofiice telephone,

system having a main ofiice station, a public telephone having a phone instrument of the French type located at said main oflice station and a cradle stand therefor, said inter-ofiice telephone system including a microphone and a sound reproducer at said main ofiice station and disposed in fixed spaced relation, and means separate of and away from said cradle stand for receiving the handle of and for supporting said French type phone instrument with its receiver adjacent said microphone and its transmitter adjacent said sound reproducer when said phone instrument is manually removed from its cradle and placed upon said supporting means by the operator to effect an acoustical connection between said French phone instrument and'said inter-ofiice telephone system.

23. An inter-ofiice system of telephonic communication comprising in combination, a main office station, a branch office station, a fixed receiver and a fixed transmitter at the main oflice station, a telephone instrument at the branch cilice system having a receiver and a transmitter arranged in fixed spaced relation relative to each other, a pair of independently operable circuits, one of said circuits having the transmitter at the main station and the receiver at the branch station arranged therein and the other circuit having the receiver at the main station and the transmitter at the branch station arranged therein.

'24. An inter-oifice system of telephonic communication comprising in combination, a main office station, a branch ofiice station, a fixed receiver and a fixed transmitter at the main office station, a telephone instrument at the branch oflice system having a receiver and a transmitter arranged in fixed spaced relation-relative to each other, a pair of independently operable circuits, one of said circuits having the transmitter at the main station and the receiver at the branch station arranged therein and the other circuit having the receiver at the main station and the transmitter at the branch station arranged therein, and switch means arranged in both of said circuits and located in the telephone instrument at the branch station for rendering said circuits operative; and inoperative by the user of said telephone instrument.

25. A system of telephonic communication comprising in combination, a public telephone system having a subscribers telephone set including a base and removable French type telephone instrument normally supported thereon, an electrically independent interofllce system having an operators station and a branch station interconnected by independently operable transmitting and receiving circuits respectively including a transmitter at one station and a receiver at the other station, an acoustical coupling device at the operators station disposed adjacent to the French telephone instrument and comprising the transmitter and the receiver of the interoflice system at the operators station disposed in fixed spaced relation corresponding to the spacing of the receiver and the transmitter of said French telephone instrument, and means for supporting said French telephone instrument in acoustical relation to the receiver and the transmitter of said coupling device when the French telephone instrument is removed by the operator from its base and placed upon said supporting means with its receiver and transmitter respectively in registry with the transmitter and the receiver of said coupling device.

26. A system of telephonic communication comprising in combination, a public telephone system having a subscriber's telephone set including a base and a removable French type telephone instrument normally supported thereon,

an electrically independent interofiice system having an operators station and a branch station interconnected by independently operable transmitting and receiving circuits respectively including a transmitter at one station and a receiver at the other station, an acoustical coupling device at the operators station disposed adjacent to the French telephone instrument and comprising the transmitter and the receiver of the interoflice system at the operators station disposed in fixed spaced relation corresponding to the spacing of the receiver and the transmitter of said French telephone instrument, means for supporting said French telephone instrument in acoustical relation to the receiver and. the transmitter of said coupling device when the French telephone instrument is removed by the operator from its base and placed upon said supporting means with its receiver and transmitter respectively in registry with the transmitter and the receiver of said coupling device, and a switch for controlling the operation of said interoffice system disposed intermediate the transmitter and the receiver of said coupling device in such position that it must be actuated into operative position before the French telephone instrument can be placed in acoustical relation with the transmitter and the receiver of said coupling device.

2'7. In a coupling device for acoustically connecting a French telephone instrument of a public telephone system with a separate and electrically independent interoflice system, the combination of a cabinet having a panel provided with a pair of openings disposed in the same fixed spaced relation as the fixedly spaced transmitter and the receiver of the French telephone instrument, another transmitter and another receiver mounted within the cabinet behind the respective spaced openings thereof, receptacles associated and in registry with said panel openings to receive the receiver and the transmitter of said French telephone instrument and support it in acoustical relation with said transmitter and said receiver of said coupling device, a control switch associated with the cabinet and switch actuating means therefor disposed intermediate said panel openings in such position as to necessitate the operation of said control switch before the French telephone instrument can be placed in operative acoustical relation with the transmitter and the receiver of said coupling device.

28. A system of telephonic communication comprising in combination, a public telephone system having a subscribers telephone set including a base and a removable French type telephone instrument normally supported thereon, an electrically independent interoifice system having an operators station and a branch station interconnected by independently operable transmitting and receiving circuits respectively including a transmitter at one station and a receiver at the other station, an acoustic-a1 coupling device at the operators station disposed adjacent to the French telephone instrument and comprising the transmitter and the receiver of the interoffice system at the operators station disposed in fixed spaced relation corresponding to the spacing of the receiver and the transmitter 01 said French telephone instrument, means disposed intermediate the transmitter and the receiver of the coupling device for supporting the French telephone instrument in acoustical relation to said transmitter and said receiver of the coupling device after'the French type telephone instrument has been removed from its base by the operator and placed upon said supporting means and switching means operably associated with said supporting means for controlling the operation of said interoffice system.

29. A system of telephonic communication comprising in combination, a public telephone system having a subscriber's telephone set including a base and a removable French type telephone instrument normally supported thereon, an electrically independent interoflice system having an operators station and a branch station interconnected by independently operable transmitting and receiving circuits respectively including a transmitter at one station and a receiver at the other station, an acoustical coupling device at the operators station disposed adjacent to the French telephone instrument and comprising the transmitter and the receiver of the interoflice system at the operators station disposed in fixed spaced relation corresponding to the spacing of the receiver and the transmitter of said French telephone instrument, means for supporting said French telephone instrument in acoustical relation to the receiver and transmitter of said coupling device when the French telephone instrument is removed by the operator from its base and placed upon said supporting means with its receiver and transmitter respectively in registry with the transmitter and the receiver of said coupling device, means disposed at said operator's station for controllably supplying energy to said receiving circuit, and signal means at the operators station rendered operative whenever energy is supplied to said receiving circuit.

30. A system of telephonic communication comprising in combination, a public telephone system having a subscriber's telephone set including a base and a removable French type telephone instrument normally supported thereon, an electrically independent interoflice system having an operator's station and a branch station interconnected by independently operable transmitting and receiving circuits respectively including a transmitter at one station and a receiver at the other station, an acoustical coupling device at the operators station disposed adjacent to the French telephone instrument and comprising the transmitter and the receiver of the interoflice system at the operators station disposed in fixed spaced relation corresponding to the spacing of the receiver and the transmitter of said French telephone instrument, means for supporting said French telephone instrument in acoustical relation to the receiver and the transmitter of said coupling device when the French telephone instrument is removed by the operator from its base and placed upon said supporting means with its receiver and transmitter respectively in registry with the transmitter and the receiver of said coupling device, and signal means at the operators station associated with both of the independently operable receiving and transmitting circuits and arranged and adapted to be inoperative when both the independently operable receiving and transmitting circuits are in use, but to become operative whenever the use of the transmitting circuit is discontinued while the receiving circuit is still in use.

31. A system of telephonic communication comprising in combination, a public telephone system having a subscribers telephone set including a base and a removable French type telephone instrument normally supported thereon, an electrically independent interoffice system having an operator's station and a branch station interconnected by independently operable transmitting and receiving circuits respectively including a transmitter at one station and a receiver at the other station, an acoustical coupling device at the operators station disposed adjacent to the French telephone instrument and comprising the transmitter and the receiver of the interofllce system at the operators station disposed in fixed spaced relation corresponding to the spacing of the receiver and the transmitter of said French telephone instrument, means for supporting said French telephone instrument in acoustical relation to the receiver and the transmitter of said coupling device when the French telephone instrument is removed by the operator from its base and placed upon said supporting means with its receiver and transmitter respectively in registry with the transmitter and the receiver of said coupling device, a loud speaker at one of said stations and selective means at said station for rendering operable either said loud speaker or the receiver of the interoflice system at said station.

32. A system of telephonic communication comprising in combination, a public telephone system having a subscribers telephone set including a base and a removable French type telephone instrimient normally supported thereon,

an electrically independent interoflice system having an operators station and a branch station interconnected by independently operable transmitting and receiving circuits respectively including a transmitter at one station and a receiver at the other station, an acoustical coupling device at the operators station disposed adjacent to the French telephone instrument and comprising the transmitter and the receiver of the interoflice system at the operators station disposed in fixed spaced relation corresponding to the spacing of the receiver and the transmitter of said French telephone instrument, means for supporting said French telephone instrument in acoustical relation to the receiver and the transmitter of said coupling device when the French telephone instrument is removed by the operator from its base and placed upon said supporting means with its receiver and transmitter respectively in registry with the transmitter and the receiver of said coupling device, a controllable electronic amplifier in the receiving circuit of said interofllce system, a signal device and switching means for energizing said amplifier and said signal device when said French telephone instrument occupies its position on said acoustical coupling device.

33. A system of telephonic communication comprising in combination, a, public telephone system having a subscribers telephone set including a base and a removable French type telephone instrument normally supported thereon, an electrically independent interofiice system having an operators station and a branch station interconnected by independently operable transmitting and receiving circuits respectively including a transmitter at one station and a receiver at the other station, an acoustical coupling device at the operators station disposed adjacent to the French telephone instrument and comprising the transmitter and the receiver of the interofiice system at the operators station disposed in fixed spaced relation corresponding to the spacing of the receiver and the transmitter of said French telephone instrument, means for supporting said French telephone instrument in acoustical relation to the receiver and the transmitter of said coupling device when the French telephone instrument is removed by the operator from its base and placed upon said coupling device with the receiver and the trans mitter respectively of the French telephone instrument in registry with the transmitter and the receiver of said coupling device, a controllable amplifier in the receiving circuit of the interoflice system, a loud speaker at said opera-,

tors station and a switch at said operators station having a neutral position in which the loud speaker is connected into the transmitting circuit of the interofiice system, an operating position in which the loud speaker is connected into 'the transmitting circuit of the interofiice system and the amplifier is energized, and another operating position in which the loud speaker at the operators station is cut out of service while the amplifier is energized.

34. A system of telephonic communication comprising in combination, a public telephone system having a French type telephone instrument normally adapted to be supported upon a cradle and embodying a transmitter and a receiver in fixed spaced relation at the opposite ends of a connecting hand grip, an electrically independent interofiice telephone system including an operators station and a branch station interconnected by independently operable receiving and transmitting circuits, the receiving circuit including the transmitter oi the interomce system at the operators station and the receiver of the interofiice system at the branch station, and the transmitting circuit includinga transmitter of the interomce system at the branch station and a receiver of the interofilce system at the operators station, an acoustical coupling device located at theoperatorsstation adjacent to and within. reach of-the French telephone instrument and embodying a panel having openings therein in corresponding spaced relation to the fixed spacing of the transmitter and the receiver of said telephone instrument, and with which openings the transmitter and the receiver of said telephone instrument are placed in registry by the operator after said telephone instrument has been manually removed from its normal position on its cradle, said transmitter and said receiver of the interofiice' system at the operators station being disposed behind said openings in acoustical relation with the receiver and the transmitter respectively or said French telephone instrument.

35. A system of telephonic communication comprising in combination, a public telephone system having a subscriber's telephone set comprising a base and a removable French type telephone instrument normally supported thereon, an electrically independent interofiice system having an operators station and a branch station interconnected by' independently operable transmitting and receiving circuits respectively including a transmitter at one station and a receiver at the other station, an acoustical coupling device comprising the transmitter and the receiver of the interoflice system at the operators station disposed adjacent and in registry with the receiver and the transmitter respectively of said French telephone instrument, a manually operable switch for rendering operable the receiving circuit of the interofiice system and mechanical means responsive to the operation of said switch for lifting the French telephone instrument slightly from its cradle to establish acoustical relations between it and the receiver and the transmitter of said coupling device.

36. A system of telephonic communication comprising in combination, a public telephone system having a subscriber's telephone set comprising a base and a removable French type telephone instrument normally supported thereon, an electrically independent interofiice system having an operators station and a branch station interconnected by independently operable transmitting and receiving circuits respectively including a transmitter at one station and a receiver at the other station, an acoustical coupling device comprising the transmitter and the receiver of the interofiice system at the operators station disposed adjacent and in registry with the receiver and the transmitter respectively of said French telephone instrument, a manually operable switch for rendering operable the receiving circuit of the interofilce system, mechanical means responsive to the operation of said switch for lifting the French telephone instrument slightly from its cradle to establish acoustical relations between it and the receiver and the transmitter of said coupling device, and means responsive to the operation of said switch for effecting the operation of a signal so long as said acoustical relation is maintained.

3'7. A system of telephonic conmiunication comprising in combination, a public telephone system having a subscribers telephone set including a base and removable French type telephone instrument normally supported thereon, an electrically independent interoffice system having an operators station and a branch station interconnected by independently operable transmitting and receiving circuits respectively including a transmitter at one station and a receiver at the other station, an acoustical coupling device at the operators station disposed adjacent to the French telephone instrument and comprising the transmitter and the receiver of the interoflice system at the operators station disposed in fixed spaced relation corresponding to the spacing of the receiver and the transmitter of said French telephone instrument, means for supporting said French telephone instrument in acoustical relation to the receiver and the transmitter'of said coupling device when the French telephone instrument is removed by the operator from its base and placed upon said coupling device with the receiver and the transmitter of the French type instrument in registry with the transmitter and the receiver respectively of said coupling de-' vice, the receiver and the transmitter at said branch station being disposed in spaced relation at the ends of a hand grip device, a normally open switch in both of said operably independent receiving and transmitting circuits disposed in said hand grip device and adapted to be held in closed operative position by the user and means controllable at the operators station for signalling the branch station.

38. A system of telephonic communication comprising in combination, a public telephone system having a subscribers telephone set including a base and a removable French type telephone instrument normally supported thereon, an electrically independent interoffice system having an operators station and a plurality of branch stations interconnected by independently operable transmitting andreceiving circuits respectively including a transmitter at one station and a re ceiver at another station, an acoustical .coupling device at the operators station disposed adjacent to the French telephone instrument and comprising the transmitter and the receiver'of the interoflice system at the operators station disposed in fixed spaced relation corresponding to the spacing of the receiver and the transmitter of said French telephone instrument, means for supporting said French telephone instrument in acoustical relation to the receiver and the transmitter of said coupling device when the French telephone instrument is removed by the operator from its base and placed upon said coupling device with the receiver and the transmitter of the French telephone instrument in registry with the transmitter and the receiver respectively of said coupling device, the receiver and the transmitter at each branch station being disposed in fixed spaced relation at the ends of a hand grip device, a normally open switch in both of said independently operable receiving and transmitting circuits disposed in the hand grip device and adapted to be held in closed operative position by the user, and a separate and independent selective interofiice signal and telephone system interconnecting the operating station and each of the branch stations.

' 39. A system of telephonic communication comprising in combination, an mteroffice telephone system having an operator's station and a branch station interconnected by independently operable transmitting and receiving circuits whereby telephonic communication may take place between the operators station and the branch station in. the conventional manner, a public telephone system having a subscribers telephone set disposed at said operators station and comprising a supporting base and removable French type telephone instrument electrically independent of said interoffice system whereby telephonic communication may take place in the conventional manner between the public telephone instrument and an outside party, and means at the operators station and including an acoustical coupling device associated with the independently operable receiving and transmitting circuits of said interoflice system for establishing telephonic communication between the interoffice system and the public telephone'system by the removal by the operator of the French telephone instrument from its normal supporting base and the placing of said instrument by the operator in acoustical relation with said acoustical coupling device.

40. A system of telephonic communication comprising in combination, a public telephone system having a subscribers telephone instrument, an electrically independent interofiice system having independently operable receiving and transmitting circuits, switching means for rendering said interoflice system operative and inoperative, means for acoustically coupling said subscribers telephone instrument and said interofiice system when said switching means is in operative position and preventing the operation of said switching means to inoperative position until such time 1

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