US2275406A

US2275406A - Intercommunication system

Info

Publication number: US2275406A
Application number: US309202A
Authority: US
Inventors: Berhley Fred
Original assignee: Individual
Current assignee: Individual
Priority date: 1939-12-14
Filing date: 1939-12-14
Publication date: 1942-03-10
Anticipated expiration: 1959-03-10

Description

March 1o, 1942.

F. BERHLEY vINTERCOMMUNIGATION' SYSTEM Filed Dec. 14, 1939 3 Sheets-Sheet l lvm March 10, 1942. F. BERHLEY 2,275,406

INTERCOMMUNICATION SYSTEM Filed Dec. 14, 1939 3 Sheets-Sheet 2 v v v v r f d J j Si o b b Q MN. NN- Nm U mw N\ .U num: .6265 @5.0mm mzaEm b w wl'. m,/r m m @Mw Si N .S a A?! 9 www mijn Nhvml am# 2E E@ 205.59V .3c @hw 6% March 1o, 1942. F. BERHLEY 2,275,406

INTERCOMMUNICATION SYSTEM Filed Dec. 14, 1939` 3 Sheets-Shea?l 3 I"Illunumunnunil!l FED BER/MEV INVENTOR ATTORNEY messed-Mar. 1o, 1942 INTERCOMMUNICATION SYSTEM Fred Berkley. Astoria', Long Island, N.v Y., assignor of forty per cent to Maxwell E. Sparrow, New

York, N. Y.

Application December 14, 1939, Serial No. 309,202

14 Claims.

The present invention relates to intercommunication systems having a plurality of stations remotely located. According to this invention some of the stations hereinafter referred to as master stations are each provided with amplifying means having input and output circuits, ear phone, loud speaker, change over switching means, earphone hook switch, selector switches speaker of the master as transmitter, amplifying y the signal by the masters own amplifier and reproducing the signal in a second masters earphone. Using the second masters loudspeaker as a transmitter, amplifying the signal by the second masters own ampliiier and using the'rst masters earphone as receiving means. Two way comunication is thus established after selecting (push button or otherwise) and a light indicator system. Other stations, hereinafter referred to as remote or sub-stations are each provided with loud speaker, selector switch and light indicator means. The loud speakers in both stations are preferably of the permanent magnet type having a voice coil suspended in a permanent magnetic eld.

It is an object of this invention to completelyv eliminate side tones in intercommunicatlon systems; that is, when one master is communicating with another, neither master can hear its own signal in its own receiving means.

A further object of this invention'is to provide a selective controllable. intercommunication system to enable interconnected stations to communicate with each other without interference from each other. A twisted cable is preferably provided to interconnect all stations.

lA still further object of this invention is to provide a light indicating system throughout an f entire intercommunication system to indicate to operators of stations which station' desires to communicate, or which stations are communicating with each other.

Another object of this invention is to provide a novel buzzer to produce an audible signal at .any station.

stations; likewise between master and remote stations, should it be so desired.

A further object of this invention is to provide an intercommunicaton system having a plurality of operating advantages by using the same type of master and remote stations for multiple operations.

The following give some of the operating advantages of this invention. l l

No. 1 master to masten-Using the loud by means of the selector switch, the second master. No further manipulation of any switches for this method of intercommunication is necessary.

No. 2 master to masten-A second method of operation, in a master to master hookup can be had by using the first masters loudspeaker as transmitting means by operating its change-over switch, and its earphone as receiving means; and the second masters loudspeaker as a receiving means for receiving the signal from the rst master and as a transmitter for transmitting tc the first master the second masterssignal with- Aout the second master manipulating any switches or controls. For this operation poweris supplied to the first master only.

No. 3 master to masten-Each master using its own amplifier and its own loud speaker as either a transmitter or receiver by simply operating the change-over switch on each master.

No. 4 master to masten-With the second master not touching any controls or switches but with the rst master controlling the second masters loud speaker circuit by its change-over switch, andthus providing the secondmaster with either receiving or transmitting means, the first master is able to receive the second masters signal either by earphone or loud speaker. This operation becomes important if one vof the units power should fail during any other mode of operation.

No. 5 master to remota-Each master being able to communicate with either its own or with any remote station common toits own or any other master. The remote station having been i provided with a selector switch to include or exclude any masters signal. Also each remote station has iight indicator means enabling it to be able to tell instantly which master is` calling. The

master communicating with a remote is able to i receive the remotes signal either byl earphone or loud speaker. The whole operation of receiving and transmitting from any remote is controllable from any master connected to the particular remote station. y

No. 6 master to master as remota-The operation between a first master and a second master can be 'hadl by operating the second master exactly like a remote with the first master, by means of a change-over switch, controlling the loud speaker circuits of both the rst master and the remote master station. It is not necessary to supply power to the amplifier of the second master for this type of intercommunication.

For any type of intercommunication, other than No. 6l the light indicator system of this invention will tell at a glance which master is originating a call and which master is responding. Also the light indicator will also tell, in a master system having a plurality of master stations, which two or more masters are in communication.

The above and further objects of the invention and the means for their attainment will be more apparent from the following detailed description, taken in `connection with the accompanying drawings, illustrating an embodiment of which the invention may be realized, and in which:

Figs. 1 and 2 show the complete circuit diagram of 2 master stations with provisions made for connecting two remote stations;

Figs. 3 and 4 show the circuit diagrams of said remote stations;

Fig. 5 shows the complete detail of an earphon hook switch;

Fig. 6 shows a change-over switch employable in the invention;

Fig. 7 shows in detail a method of mounting the earphone hook switch and the change-over switch; Y

Fig. 8 is a rear view of a remote station selector switch; and.

Fig. 9 is a front View of Fig. 8.

The rotary selector switch shown in Figs. 8 and 9 is preferably a special type snorting switch.

one position 45B allows all masters connected to this switch to call the remote station and in other positions 65C, l35D, etc.'(Figs. 3, 4) to exclude any unwanted master station.

' The rotary selector switch shown in Figs. 8 and 9 consists of a single deck of insulating material D with a number of contacts points I-II) mounted in front and in rear of the deck, a front and an opposite rear contact being held together by means of a single rivet R and electrically shorted together, with their common terminals 65A and lB joined together by a conductor.

In the position shown in Figs. 8 and 9 the switches are in the all position, meaning that any master connected to this switch at the points l-I, respectively, by means of an interstation conductor can call the remote station.l

If, then, a master calls a remote station the operator of the remote can tell by means of the indicator light which master is calling and may then turn by means of shaft H of his switch S to the calling masters conductor connected to one of the points l-i thus excluding all other masters from communicating with this remote until remote has nished the rst masters communication. The second master, however, can identify his call by flashing on his light indicator leaving on his light until the remote answers his call or if an urgent message must be transmitted to the remote can identify his call by a series of pre-arranged flashes.

`lit is evident from the above and by an examination of Figs. 3 and 4. of the drawings that any remote, common to a number of masters is selective in respect to the masters, meaning that the remote can select any masters incoming and any remotes outgoing signal; also any masters outgoing and any remotes incoming signal as far as master to remote station operation is concerned.

Detail of the various operating methods y Figs. 1 and 2 show a complete circuit diagram of two masters and station .conductors to two remote stations. Figs. 1 and 2 are the two masters in normal or receiving position, with power supplied to the masters, lever 8 in N or normal position, all push buttons released or in out position and being designated by the numerals 20, 2I, 22, L23, 24 and 25. The earphone I5 is suspended from earphone hook switch 5. The weight of the earphone will close leaves 5B and 5C.

The common terminal 1A of change-over switch 6 engages contact IC through feeder F and common terminal 'IE engages contact 1G through feeder F. A lever knob 8 is attached to shaft 8' of the change-over switch 6.

The lever 8 carries a small extension rod or bar 'I'. A short piece of elastic or felt material 'l is slipped over and fastened in place on rod or bar 'I'. This is done in order to prevent any clicks or mechanical noise being produced, when lever 8 is operated and in certain positions strikes the earphone hook 5. The amplifier 9 is a standard device with its own power supply indicated at I0, but not shown. The amplifier. has been provided with an input transformer II-I8 and an output transformer I2-I3. The secondary of input transformer I1 connects with one side to the ampliflers ground lead the other side of the secondary to the signal grid of the first vacuum tube (not shown) of the amplifier. The primary side of the output transformer I2 connects with one side .to the plate of the last or power tube (not shown) of the amplifier andthe 40' The numeral I4 indicates the loudspeaker dia-- phragm. The earphone I5 is of a suitable impedance and the volume limiting resistor I6 is directly shunted across the earphone and is lof a predetermined value. The condenser iI is of a suitable value and -is connected between the ground lead of the amplifier and the common conductor 9i, this being done in order to eliminate stray coupling or capacity effects in the intercomrnunication system.

The selectors are shown as push buttons 2G, 2l, 2E and 23 of the conventional lock type holding their position when depressed and may be released by button 25. Button 28 is a simple spring return push button and is used for connecting feedback condenser I9 between the plate side of the output transformer primary I2 to the signal grid input side of input transformer I 1A. Depressing button 24 will cause a certain amount of energy to be fed back from the output of the lamplifier 9 to the input of the amplifier 9 and in audible note will be heard in any remote station that may be connected to this master and selected by the station selector push button. This constitutes the audible buzzer system. Push button 24 -is independent of all other buttons.

Contacts 20A and 20C are mechanically coupled to button 20 though electrically insulated from each other. Likewise 2IA and 2IC; 22A

pressed cause contacts between 20A- 20B and 20C-2 0D, simultaneously; 2 IA-2 IB and 2 IC-2 ID, simultaneously; 22A-22B and 22C-2 2D, simultaneously, 22A-2 3B and 23C-23D, simultaneously.

Pressing push button 24 causes contact betweenV 24A and 24B. This push button Varrangement provides station selection and light indication in the present intercommunication system.

Terminal strip 50 carries the conductor` terminals 31, 3|, 32, 33, 34, 35 and 36.

Contact points 20C, 2|C, 22C, 23C are connected in parallel and to one side of the power line. Contact points 20D, 2ID, 22D and 23D also connect in parallel but to one side of primary 26 of the light indicator supply transformer. The other side of primary 26 connects to the other side of the power line. The secondary side 21 of the supply transformer connects directly to a small rectifier 28 of the oxide type, having sufficient capacity for the purpose intended. The negative side of the rectifier connects directly to the common lead conductor 31. The positive side of the rectifier connects to one side of pilot light indicator 29 and to terminal 32 on terminal strip 56 in Fig. 1 (master station No. 1); the

other side of indicator 29 connecting directly to common conductor 31. Pilot light indicator 30 also connects to the common 31 with one side and with the other side to terminal 3| on terminal strip 50. This provides the light indicator system for power line operation. If this system is to be battery operated then a suitable battery supply must be substituted for transformer 26 vand 21 and rectifier 28 withthe following changes in wiring. The negative of the battery supply will have to be connected to the common lead 31, buttons 20C, 2IC, 22C, 23C being still connected in parallel but going to the'positive terminal of the battery supply, and buttons 20D, 2|D, 22D, and 23D still connected together but connecting to the side of the pilot vlight indicator 29 that formerly connected to the positive terminal of rectier 28. In Fig. 2 (master station No. 2) the positive supply from either rectifier or battery connects to one side of pilot light All stations are interconnected by the following conductors. Conductor 31A from terminal 31' of master station No. 1 (Fig. 1) to terminal 31' on master station No. 2 (Fig. 2) and to terminal C on remote stations Nos. 1 and 2 (Figs.

3 and 4). Conductor 3IA from terminal 3|. of master station No. 1 to terminal 3| of master station No. 2 and to terminal 42 of remote stawishes to call master station No. 2, it being, however, understood that power is supplied to both master stations.

Now, if the earphone I5 is lifted oi the earphone hook 5', leaf 5A contacts leaf 5B. A conductor 65 connects 5A-5B to common terminal 1E on change-over switch 6 through a common feeder F to contact points 1F and 1G of switch 6 and from 1F--1G through conductor 66 to pushbutton contact 20B and from there through conductor 61 to terminal 33 on strip 50 of master station No. 1, Conductor 33C connectsA master station No. 1 to terminal 33 on master station No. 2. Conductor 68 connects terminal 33 on master station No. 2 with pushbutton contact 2IB. Conductor 69 connects contact 2IB with contact points 1G and 1F of switch 6 on master station No. 2 and through a common feeder F' to common terminal 1E of switch 6 on master station No. 2. The conductor 65 from 1E of master station No. 2 'continues toleaves 5B-5C of earphone hook 5 of master -station No. 2, leaf 5C being connected to leaf 5D, also through conductor 1II to one side of the loudspeaker I4. The other side of loudspeaker I4 connects to the common conductor 31 of master vstation No. 2 then to terminal 31 on terminal strip 5U of master station No. 2, the common conductor 3| then retions Nos. l-and 2. Conductor 32B from terminal '32 of master station No. 1 to terminal 32 of master station No. 2 and to remote station No. 1 terminal 4|; alsol remote station No. 2 terminal 4| of conductor 32B from terminal 33 of master station No. 1 to terminal 33 of master station No. 2. Conductor 34D from terminal 34 of mas- `ter station No. 1 to terminal 34 of master station No. 2. Conductor 35E of master station No. 1 to 43 of remote station No. 1 and conductor 36F from terminal 36 of master station No. 1 to terminal 43 of remote station No. 2. Conductor 36' from terminal 35 of master station No. 2 to terminal 440i remote station No. 1 and conductor 36' zfrom terminal 36 on master station No. 2 to terminal 44 of remote station No.2.

Let it be assured that master station N6. 1 'la with the common lead 31.

turns to master station No. 1 through conductor 31A. Referring back to earphone hook 5 of master station No. 1, it is to be noted that leaf 5A is connected to one side of theearphone I5, the other side of earphone I5 connecting directly shunted directly across the earphone I5 at all times. Upon' lifting of earphone I5 from hook 5' leaf 5B disengages from leaf 5C and engages or contacts with leaf 5A, leaf 5D making contact with leafv 5E. Leaves 5C and 5D are connected together and by conductor`10 to one side of loudspeaker I4, the other side of the loudspeakery connecting with common lead 31. Leaf 5D having made contact with leaf 5E now carries one side ofthe loudspeaker I4 through a coductor 1I to one side of the input transformer primary. I8 and to contact 1D on change-over switch 6. The other .side of the input transformers primary I8 connects with the common lead 31. One side of the output transformer's secondary I3 connects with the common lead 31, and the other side thereof with contact points 1B, 1C, and1H on switch 6 through conductor 12, the latter also connecting with a common feeder to common terminal 1A on switch 6 and with a conductor 13F to pushbutton contact points 20A, 2IA, 22A and 23A.

Depressing pushbutton 2| of master station No. 1 will close and lock in position respective contact points 2|A-2IB and 2|C-2|D. A conductor 14 connects contact point 2IB with terminal 34 on terminal strip 56 of master station No. 1. Conductor 34D conects master station No. 1 with terminal 34 of master station No. 2, and continuing to pushbutton contact 2IB of master station No. 2, then through a conductor 69 to contact points 1F and l1G on switch 6 of master station No. 2 and through common feeder F from contact point 1G to common terminal 1E, common terminal 1E through conductor 65 connects with earphone hook leaf 5B, leaves 5C-,5D. Leaves 5C5D are connected together and through conductor 10 to one side of loudspeaker I4 of master station No. 2. The other side of loudspeaker I4 connects with common lead-31. Having depressedbutton 2| on master station No.

The resistor I6 isv 1 thus closing contacts 2IA-2IB and 2|C-2ID and applied the power line voltage across the light indicator transformer's primary 26,-a secondary voltage is induced in secondary 21 and is fed into the input of the oxide type rectifier 28. The negative terminal of the rectifier connects with the common lead 21. The positive terminal of the rectifier connects with one side of the pilot light 29 and to terminal 32 on terminal strip 50. In master station No. 2 the positive side of the rectifier 28 connects with-pilot light 30, and with terminal 3| on the terminal strip 50. Terminal 32 of master station No. 1

connects through conductor 32B with terminal 32 on master station No. 2 and with one side of pilot 29. formers primary '26 in master station No. 1 by depression button 2 I, will cause pilot light'29 thus closing contacts 2IC and ZID in master station No. 1 and likewise pilot 29 in master station No. 2 to light up. If master station No. 1 now has its buzzer push button depressed an audible note will be heard in the loudspeaker of master station No. 2, due to the feed back capacity I9 being connected to push button contacts 24A-24B and to input transformer side IIA. The pilot light constitutes this systems visual, and the buzzer its audible, indication of a stations call. Now if the earphone I of master station No. 2 is lifted off the hook 5' and the operator o f master station No. 2, knowing by prearrangement that his pilot 29 belongs to master station No. 1, depresses his pushbutton 20, thus closing pushbutton contacts A-20B and 20C-20D, he will cause his pilot light 30 and pilot light 36 in master station No.A 1 to light up, indicating to master station No. 1 that master station No. 2 is ready for communication, because the exact electrical action has taken place in master station No. 2 as has been described with relation to master station No. 1, when the earphone on master station No. 2 was lifted off the hook.

To sum up, the: action which takes place in both masters are as follows: The loudspeaker of each master station is now used as a transmitting means and is placed across the input transformer of` each master stations amplifier, but the output transformer I3 of master station No. 1 is connected across the earphone of master station No. 2 and the output transformer VI3 of master station No. 2 has been connected-across the earphone of master station No. 1. Two-way communication has thus been established without further manipulation of any switches. When communication has been completed both masters press their respective release buttons 25, and

-replace the earphones thus restoring the master stations tov their original or normal position and ready for another call.

It is evidentgfrom theY above vdescription that an`intercommunication system has been provided with absolute privacy during communication between two master stations and no other master station that may be connected to the same system can possibly listen in. i It is also evident that the system is not limited to two master stations but by simply adding interstation conductors, terminal posts, pilot lights, station selector pushbuttons, any number of master stations may be incorporated in an intercommunication system.

A second operation -with'the same master stations is possible, using loud speaker to loud speaker between 2 master stations as described heretofore in paragraph numbered 3. Again sta- Applyingva line voltage across trans-.

tion selection must be'xnade by depressing and locking pushbutton 2|, after supplying power to both master stations and again pilot light 29 will flash on in master station No. 1 and master station No. 2. Now the operator of master station No. 1 does not have to lift the earphone I5 of the earphone hook 5 but presses lever 8 on switch 6 into its lowermost position designated as T, or talk position and thereby lifts the earphone hook, just high enough to again close leaves 5A and 5B and leaves 5D and 5E of earphone hook 5 by means of extension rod 'II attached to lever 8. It is also evident that the conductor from

pushbutton contacts

20A, 2|A, 22A and 23A and connecting to the common terminal contact IA on change-over switch 6 and has been transferred by means of a common feeder F from contact 'IC to contact 'ID and to input transformer I8; also to leaf 5E and leaf 5D, leaf 5D having made contact with leaf 5E, by pressing lever 8. Therefore loud speaker |4 being connected to leaf 5D has been placed against across the input transformers primary I8. When lever 8 was pressed into its lowermost position T, common feeder F from common terminal lA moved away from 'IC to contact 1D and common feeder F1 from terminal IE moved away from contact `IG` to contact 1F, thus freeing contacts 'IB and 7C and contacts 'IF and 1G. Contacts 'IH-'IB and IC being connected together and to output transformer I2 are now connected through common feeder F to terminal 'IA and by a conductor '13, to pushbutton contacts 20A, 2IA, 22A, and 23A; and having depressed and locked button 2| and thereby closing contacts 2IA and 2 IB,

and continued from button contact 2IB through conductor 14 to terminal 34 and by conductor 34D to terminal post 34 of master station No. 2 and on to button contact 2IB through conductor 69 of master station No. 2 and to contact point 'IG through common feeder F to terminal point 'IE and by conductor B5 to leaf 5B through contact 5C and byconductor 10 to loud speaker I4 of master station No. 2. Both master stations being connected also by the common conductor 31A, it is evident that loud speaker I4 of master station No. 2 is still placed across the output transformer I3 of master station No. 1. Master station No. 1 now uses his loud speaker as transmitting means and amplifying its signal by means of amplifier 9 reproduces its signal in loudv speaker I4 of master station No. 2. When master station No. 1 has nished a call, master station No. 2 operates lever`8 in the same manner as has justV been described for master station No. 1. It is, of course, understood that master station No. 1 has lever 8 returned to N or normal position leaving button 2| depressed and locked until all messages have passed between the two master stations. If master station No. 2 depresses andlocks button 20 pilot light 30 will light up'in'both master stations No. 2 and No.1. Depressing lever 8 on master station No. 2 to the lowermost position results in the exact electrical action as has been described for master station No. 1, except that master station No. 2 uses loud speaker I4 for transmitting means and loud speaker I4 of master station No. 1 as reproducing means for the amplified signal from master station No. 2 again through common conductor 31A and conductor 33C from terminal 33 on master station No. 2 to terminal 33 on master station No. 1. Two-way loud speaker communication between two master stations has thus been provided. It is also evident that either master station may receive the incoming signal either by earphone or loud speaker, if so. desired and by operating the change-over switch as mentioned lsecond master station operating its controls or veven turning on its power. This operation becomes important if the power should fail in any master station. With power supplied to master station No. 1 pushbutton 2| is again depressed and locked in position. This again closes conremote station is essentially the same as has been described for master stationv to master station l operation with the second master station not operating any controls. Remote stations may be connected either to respond to one `master station only or as shown in the drawings. common to all master stations. Remote station No. 1 .connects to master station No. l by means of conductors 35E. vcommon conductor 31A and 34D to pushbutton contact 2 IB on master station No. 2 and to contacts 'IG and IF on switch 8 of I master station No. 2, through common feeder F to contact'IE and to switch leaf 5B closing through contact 5C loud speaker. lI4 to common conductor 3l on master station No. 2. Returning to master station No. 1 it is evident that the conductor v'I4 from pushbutton contact 2IB is carried, by previously having locked 2IA and 2IB, to terminal point 1A on switch 6, through common feeder F to contact 1C, with contact IC connecting to output transformer I3 and to common'conductor 3l.l It is evident that loud speaker I4 of master station No. 2 now has been placed across the output transformer of master station No. 1 and is used as the reproducer for any signal coming from master station No. 1. If lever 8 of master station No. 1 is now again pressed into4 `its lowermost position, earphone hook EI will be conductor 82B, master station No. 2 connects 'also to remote station No. 1 by conductors 31A,

35 tand 3IA. Remote station No. 2 connects to master station No. 1 by conductors 31A, 32B and 86F. Master station No. 2 connects to remote station No. 2 by means of conductors 31A, 8IA and 36'. If master station No. 1 wants to call remote station No. 1, the lever 8 of master stationvNo. 1 must be pressed against into vits lowermost o r talk position, button 22 must be pressed and locked in position; then loud speaker 38 of remote station No. l will be placed across the output transformer I3 of master station No. 1 by means of

conductors

31A and 35E, contact 45D on switch 46 in remote station No. 1 and through its

common terminals

45A and 45B.

. Pilot light.4ll will flash on by means of common conductor 81A and 32B. Figures 38Aand38B only signify -start andflnish of speaker winding and have no other meaning. It should be mentioned that power must be supplied to a master station wishing to communicate with a remote station. With switch S on the remote station in all positions as shown, it is entirely possible'for all malster stations to call the remote station No. 1 at the same time. `While this feature is desirable it is not entirely practical, for the following reason:

. Should remote station No. il be in .transmitting ter station No. 1 can now transmit its signal to master station No. 2. In order to receive a reply from master station No. 2, lever 8 of master station No. 1 must be lifted to its uppermost or listen position L. The following takes place. The earphone hook 5' will be restored to normal position by weight of earphone, common feeder F' will move from 'IG to 'IF thus placing loud speaker I4 of master station No. 2 across the input transformer of master station No. l and loudspeaker I4 of master station No. l across the output transformer I2 of master station No. l. It is now clear that by pressing lever 8 on mas- 1 ter station No. l into the lowermost or talk position, master station No. 1 loud speakers will be used as transmitting means and loud speaker I4 of master station No. 2 will be used as reproducing means, and with lever 8 of -master station No. 1 in its uppermost or listenposition, loud speaker I4 of master station No. 2 will be used as transmitting means'and loud speaker I4 of master station No. l will be used as reproducing means. 'I'he above confirms with paragraph 4, the buzzer operates in the usual manner by depressing button 25 and letting button return to normal.

` The next operation possible with this system, is in a master station' to remote station hookup as mentioned hereinbefore in paragraph numbered 5. The operation between a master station and a position to master station No. 1 and master station No. 2 in transmitting position to remote station No. 1, the total output of master station No. 2 along with the signal from remote station No. 1 would appear at the input of master station No. 1, resulting in such tremendous ampliiication, as to set up a howl or even render the whole system inoperative. Therefore, switch S has been provided to eliminate this. possible interference. When master station No. l calls remote station No. 1, the pilot light 40, as stated before, will ash on and a buzzer signal will be heard in loud speaker 38 of remote station No. 1, informing the operator of remote station No. l by visual means of pilot light 49 that master station No. l wishes to communicate.

or more master stations should it be necessary,y

by manipulating selector switch S and without interference from or between master stations. The same action as described for master station `No. 1, will take place-ifl master station No. 2

should call remote station No. 1, but then pilot light 39 will ash on and operator of remote,

station No. l must set his selector switch S to contact 45C in order to exclude any other master station. After nishing communication'with any master station, operator of remote station No. l returns his switch S to the all position 45B e mote station No. 1.

n' rder to allow any master station to call re- It is evident from the above descriptionl that the loud speaker 38 of any remote station is alternately used as transmitting and reproducing means, remotely controlled by switch 6 of any master station connected to the remote station, land also that any master station in communication with any remote station can receive the signal of the remote station at the master station using either the earphone I or the loud speaker I4 of the master station as reproducing means. After completing any call, release button 25 must be pressed to restore all circuits to normal.

A still further type of operation possible with this system and as mentioned hereinbefore in paragraph numbered 6 is as follows: Master station No. 1 may call master station No. 2 operating master station No. 2 as outlined before with l no power applied to master station No. 2 and 0perating remote station exactly as outlined under master station vto remote station operation with switch 6 and push-buttons 2l, 22 or 23 of master station No. 1the controlling factor in this type of operation. Again the loudspeaker of master station No. 2 and the loud speaker of any remote station are used alternately as reproducing and transmitting means.

Thus there has been provided an eiiicient intercommunication system with audible and visual signals at remote master stations and remote substations. thus minimizing manufacturing and electrical difficulties, and with an unlimited amount of master and remote stations operation in a system without interference from and between each other.

It is, of course, understood that this system is' not limited to the number of master and remote stations shown in the drawings but may be extended to include any number of stations by adding additional selector and light-indicator means, terminals, interstation conductors, pilot lights, etc.

In the accompanying drawings there is illustrated the invention embodied in one of its practical forms but as this illustration is primarily for purposes of disclosure it will be understood that the invention is not limited to this vparticular form of structure and that it may be modified in many respects without departure from the true spirit and scope of theinvention as herein defined and claimed. It is further understood that the terms which are employed herein are used in a descriptive rather than in a limiting sense, except, however, for such limitations that may be imposed by the state of the prior art.

Having thus described the invention what is claimed as new and desire to secure by Letters Patent, is:

l. In an intercommunication system the combination including a plurality of stations each station having loud speaker means, amplifying means and an earphone; means for using the loud speakermeans of each station as a transmitter, said amplifying means of one station for amplifying the signal of said one station and simultaneously reproducing said signal in the earphones of the remaining stations, means'for selecting for communication any one of the said remaining stations, and indicating means for each of said stations for indicating the origin of a signal from any of said plurality of stations.

2. In an intercommunicating system the combination including a plurality of stations each station having loud speaker means, amplifying means, station selector switching means, and switching means for transferring the loud speaker means of one station from reproducing position to transmitting position and simultaneously reproducing the signal of said one station in the loud speaker means of the remaining stations, means for selecting for communication any one of the said` remaining stations, ,and indicating means for each of said stations for indicating the origin of a signal from any' of said plurality of stations.

3. In an intercommunicating system the combination including a plurality of stations each station having loud speaker means, amplifying means, switching means, means for alternately using the loud speaker means of one station as its transmitter and as reproducer for the signal from the remaining stations, station selector switching means for selecting for communication any one or all of said remaining stations, and

indicating means for each of said stations fory indicating the origin of a signal from A any of saidplurality of stations.

4. In an intercommunicating system the combination including a plurality of stations each station having loud speaker means, at least one station having .amplifying means, switchingl ing means in another position `conditioning the loud speaker of said selected station as a transmitter for the amplifying vmeans of said one station and the loud speaker means of said one station as reproducing means for the signal from the said selected station, and indicating means for each of said stations for indicating theI origin of la signal from any of said plurality of stations.

5. Inan intercommunicating system the combination including a plurality of stations a first number of said stations having loud speaker means, amplifying means, earphone, earphone switch means and station selector switch means, a second number of said stations having loud speaker means and station selector switch means, the station selector switch means of one of said second number of stations being operable in one position for selecting an incoming signal from one of said first number of said stations and an outgoing signal from said second number of said stations to one of said first number of said stations and being operable in another position for permitting communication between one of said second number of said stations with one or all of said first number of said stations.

6. In an intercommunicating system the combination including a plurality of stationsa fi'rst number of said stations having loud speaker means, amplifying means, earphone, earphone switch means and station selector switch means, a second number of said stations having loud speaker means and station selector switch means, the station selector switch means of one of said second number of stations being operable in one position for selecting an incoming signal from one of said first number of said stations and an outgoing signal from said second number of said stations to one of said first number of said stations and being operable in another position for permitting communication between a second number of said stations having loud speaker means and station selector switch means, the station selector switch means of one of said second number of stations being operable in one position for selecting an incoming signal from one of Asaid first number of -said stations and an outgoing signal from said second number of said stations to one of said first number of said stations and being operable in another position for permitting communication between one of said second number of said stations with one or all of said rst number of said stations, indicating means for indi'catingin said one of said second number of said stations vwhich stations are communicating with each other or which of said first number of said stations desires to communicate with said one of said second number of said stations, and audible signall means for indicating to said station of said second number of said stations which of said first number of said vstations desires to communicate with said station of said second number of said stations.

8. In an intercommunicating system the combination including a plurality of stations a first number of said stations having loud speaker means, amplifying means, earphone, earphone switch means and station selector switch means, a second number of said stations having loud speaker means and station selector switch means, the station selector switch means of one of said second number of stations being operable in one position for selecting an incoming signal from one of said first number of said stationsand an outgoing signal from said second number of said stations to one of said first number of said stations and being operable in another position for permitting communication between one of said second number of said stations with one or all of said first number of said stations, indicating means for indicating in said one of said second number of said stations which stations f are communicating with each other or which ofv said first number of said stations desires to communicatewith said one of said second number of said stations, audible signal means for indicating to said station of said second number of said stations which ofsaid rst number of said stations desires to communicate with said station of said second number of said stations, and conductorsconnecting said stations, said conductors including a common conductor for receiving and transmitting.

9. In an `intercommunicating system the combination including two stations, each having amplifying-means, loud speaker means adapted to be used both as a receiver and a transmitter, an earphone and earphone hook switch; a communication circuit between said amplifying means, loud speaker means, earphones and earphone hook switches, said circuit ,including interstation conductors connecting said stations with one of said conductors acting as a common conductor for receiving and transmitting, a second of said conductors completing the communication circuit between the amplifying means of one station and the receiving means oi the other station, and a third conductor completing the communication circuit between said other stations amplifying means and the receiving means of said one station.

l0. In an intercommunicating system the corn-` bination including a plurality of stations, each having amplifying means, loud speaker means adapted to be used both as a receiver and a transmitter, a station selector switch, an earphone and earphone hook switch; a communication circuit between said amplifying means,

loudspeaker means, station selector switches,-

-ing means of one station and the receiving means of another station, and a third conductor completing the communication circuit between said another stations amplifying means and the receiving means of said one station; and a change-overswitch for each station, said changeover switch being connected with earphone, earphone hook switch, loud speaker means, amplifying means and to selector switch for selectively using the loud speaker means of said stations as receiving or transmitting means.

11. In an intercommunicating system the combination including stations, each having amplifying means, `loudspeaker means, earphone, an

earphone hook switch, a change-over switch a selector switch, and light indicating means; a communication circuit between saidA amplifying means, loud speaker means, station selector switches, earphones, earphone hook switches, said circuit including interstation conductors connectingv said stations with one of said conductors acting as a common conductor for receiving, transmitting and indicating,` a second of said conductors completing the communication circuit between the amplifying means of one station and the receiving means of another station, a third conductor completing the communication circuit between said another stations amplifying means and the receiving means of said one station, a fourth conductor completing the indicating circuit from one station to said another, and a fifth conductor completing the light indicating circuit from the said another station to the said one station, said indicating means being operable simultaneously with the station selector switch to indicate which of the stations are in communication in the system.

12. In an intercommunication system, the combination including two stations, first and second respectively, a transmission circuit between the rst station and the second station, a transmission circuit between the second station and the first station, each circuit including a loud speaker used as a transmitter, an earphone used as a receiver, an earphone hook switch, an amplifier, input means to said ampliner, output means from said amplifier, and selector switch'means; said transmission circuits including a common conductor connecting with one side of the loudspeaker, earphone, output means and input means, the selector switch means of one of said stations for closing the transmission circuit of the other of said stations through its receiving means.

13. In an ntercommunicating system the combination including two stations, each having amplifying means, loudspeaker means adapted to be used both as a receiver and a transmitter; a communication circuit between said amplifying means and loudspeaker means, said circuit including interstation conductors connecting said stations with one of said conductors acting as a common conductor for receiving and transmitting, a second of said conductors completing the communication circuit between the amplifying means of one station and the receiving means of the other station, and a third conductor completing the communication circuit between said other stations amplifying means and thereceiving means of said one station.

14. In an intercommunicating system the combination including a plurality of stations, each having amplifying means loudspeaker means adapted to be used both as a receiver and a transmitter, a station selector switch; a communication circuit between said amplifying means, loudspeaker means and station selector switches, said circuit including interstation con-l plifying means and the receiving means of said one station; and a change-overswitch for each station, said change-over switch being connected with loudspeaker means, amplifying means and to selector switch for selectively using the loudspeaker means of said stations as receiving or transmitting means.

FRED BERHLEY.