US2561946A

US2561946A - Intercommunication system

Info

Publication number: US2561946A
Application number: US164336A
Authority: US
Inventors: Pedatella Frank
Original assignee: Individual
Current assignee: Individual
Priority date: 1950-05-26
Filing date: 1950-05-26
Publication date: 1951-07-24
Anticipated expiration: 1968-07-24

Description

y 24, 195] F. PEDATELLA INTERCOMMUNICATION SYSTEM Filed May 26, 1950 INVENTOR. Frank Pedcliel [0 ATTORNL f5,

Patented July 24, 1951 UNITED STATES PATENT OFFICE I 2,561,946 INTEROOMMUNICATION SYSTEM Frank Pedatella, New Kensington, Pa.

Application May 26, 1950, Serial No. 164,336

Claims.

This invention relates generally to communication systems, and more particularly to su h systems embodying a plurality of transducer stations which may be selectively connected together.

This invention, while primarily adapted for, and illustrated in connection with, a direct wire type of intercommunication system,. embodies certain fundamental aspects which are useable in other types of circuits. However, it will be appr'eciated that in the illustrated system,-repre senting a preferred embodiment of the invention, a degree of simplicity is achieved which is not to be found in more conventional apparatus for the intended purpose.

' In the usual intercommunication system each master station is provided with equipment including an amplifien'a transducer, usually in the form of a permanent magnet speaker, or, alternatively, a separate speaker and microphone, together with a push button station',-the push button station being operated selectively to connect the corresponding master station with other master or staiT stations forming a, part of the system. Suitable relay switching means under the control of the respective master station push buttons establish the desired circuit connections. W Each master station with its amplifying and switching units represents a complicated and expensive piece of equipment. As a consequence, in installations embodying such equipment, the master station installations are limited to those points from which control and direction of operation is to reside, while the remaining stations, usually referred to as stafi stations, are equipped only with a transducer unit completely under the control of the master stations.

In numerous instances, situations arise at the various stafi' stations which require contact with personnel at one or more master stations,.but with such a system the staff personnel has no means through the intercommunication system for contacting the desired master station personnel. This, of course, is a, limitaton which re stricts the effectiveness of the system.

Accordingly, one object of this invention is to ,provide an intercommunication system of sim:

plifled and economical structure, a, system which may be installed easily and operated readilysystem which is positive in operation. 7

Another object of this invention is to provide an intercommunication system in which a cen-.- tral amplification system is employed. It is also an object of this inventionto provide a system of the character referred to, whose ment of, the invention.

While it will be appreciated that the intercom- .munication system illustrated in the drawin may incorporate any number of stations, four stations are illustrated in this case, since the structure of the invention and its operation may be fully understood with such showing. The four stations are shown respectively designated SI S2, S3 and S4. Each includes a transducer element illustrated in block diagram and identified by the reference characters Ti through T4, respectively. Each transducer embodies conventional equip- .ment. For example, the transducer'may consist of a standard permanent magnet speaker which may be utilized to convert electrical signals to sound, and, conversely, may be utilized to conv-ert sound or speech to electrical signals. A1- ternatively, of course, a transducer in each case may include a separate speaker and a separate microphone suitably connected into the system for the intended purpose. Other arrangements may be incorporated for accomplishing the intended purposes, by means of other forms of conventional apparatus.

Each xstation also includes a plurality of switches, one switch for each station. In station SI these switches are designated SH through SM. In station S2 the switches are designated SZI through S24. In station $3 the switches are designated S3! through S34, and in station S4 the switches are designated SM through S44.

Selective switching for interconnecting the desired transducer elements is accomplish-ed by a pair of switch assemblies M and SS. Switch assembly MSS is a master station selector switch, and switch assembly SS'is an auxiliary selector switch which-Works in conjunction with the master selector switch MSS to provide connections between the desired transducers. Both switch assemblies are motor operated, switch MSS being driven by a, motor IM and switch SS being driven by a motor 2M.

Referring particularly to the master switch arrangement, the master switch includes four separate switching units, one for each switch station. These separate units are shown as interconnected mechanically operated switch stacks, having an operating member which rides on the surface of a cam ii). This cam is circular in configuration and has a single projection H thereon, which during cam rotation successively engages the operating members of the separate switch stacks, and thereby operates these separate stacks. The cam is shown to be mechanically connected to the motor IM, and this connection is to be understood to include a reduction gear assembly, if required. Control of the motor IM, which operates the separate switch units, is obtained by suitable interlocking of the motor, circuit with normally closed switches iMl through wi l which are disposed on the respective switch units. These separate switch units have a common terminal connected to one terminal of the motor IM, the other terminal of the motor IM being connected to the line 2 of the power supply lines I and 2. These supply alternating current (although the apparatus may be designed for direct current) for operating the system. A normal 110 volt A. C. power supply will do.

Each of the switch units of the respective switch stations is illustrated as a three terminal switch. Refer, for example, to the switch SH. This switch includes the terminals or contacts Ila, Nb and Ho which are straddled by a mov able contact member which is push-button operated, and which in its closed position, under manually applied pressure, engages all three of the named contacts. The middle contact, Nb, of switch SH is connected to the power supply conductor l, and similarly the middle contact of each of the remaining switches of all of the stations is also connected with the power supply conductor I. Thus, in efifect, there are provided with the three terminals, two switches which are simultaneously closed at the time the push-button is operated.

Control of the motor lM is obtained from the respective stations Sl-S4, by connecting certain switch terminals thereof to corresponding terminals of the respective switches designated 1M! through lM4. For example, the terminals Ha, l2a, Ilia and lid of station Si are connected in parallel by means of a common conductor to one of the two contacts of the switch lMl. The corresponding terminals of switches S2! through S24 of the station S2 are connected in parallel to one contact of switch !M2; the corresponding terminals of the switches S3! through S34 of station S3 are connected in parallel to one contact of switch 1M3; and the corresponding terminals of the switches SM through S44 of station S4 are connected in parallel to one contact of switch IM4. Th remaining contact of each of switches iMl to [M4 are connected in parallel to one terminal of the motor lM, as shown.

Returning to the switch Sli of station Si, it will be appreciated that by depressing the push button of this switch a circuit is completed from the conductor 4 through the contact i lb and contact Ha to one contact of the switch IMI. Assuming that the cam 59 is in a position different from that illustrated. it will be understood that n th contact IM! will be in circuit-closing position. Thus, both contacts of the switch I Ml will be electrically united, whereby electric supply line I is connected to one terminal of the motor WI. The other terminal of motor lM is permanently connected to the electric supply line 2. Thus, the energizing circuit for the motor is completed.

The motor IM rotates in one direction only, which in this case is clockwise as viewed in the drawing. It will be understood that th cam It will be rotated until the projection H thereof engages the operator of the switch stack including the contact arm of switch I MI. At this point the switch IMI is opened and the energizing circuit for the motor lM' is interrupted and the motor stops. The operation involving the control of the motor IM for the remaining switches S12 through SM on station SI is the same, since closure of any one of these switches establishes an energizing circuit for the motor through the contacts of switch iMl. Thus, regardless of which of the motor operating contacts on station Si is manually operated, the motor will always stop with the cam in the position illustrated in the drawings.

This same type of operation is effected from any of the remaining switch stations. For exams ple, referring-to station S 1, the closing of switch S4! completes an energizing circuit for the motor !M, the circuit running from the conductor I through the contact Mb to the contact Ma, and from the latter contact through the two contacts of the closed switch !M4 to on terminal of the motor !M, the circuit being completed from the other terminal of the motor I M to the conductor 2. Assuming that at the time this energizing circuit is; completed the cam Ill is in the position illustrated, the motor 1M will rotate the cam clockwise, until projection ll thereof engages the operator of the switch stack including the switch IMA'. At this time the contact IMA is opened and the energizingcircuit for the motor is brokern From the foregoing it will be appreciated that operationof any one of the push buttons hereinabove considered in the respective stations S l-S4 will cause operation of the motor IM to actuate the switch unit corresponding to the stationon which the particular push button switch has been operated, thereby eiiecting selective'operation'of the switch units of the master switch 'MMS.

As earlier noted herein, the auxiliary selector switch SS is operated by a motor 2M. The motor 2M is controlled by a switch arrangement corresponding to the switch arrangement IMI through 1M4 of the master switch. This switch arrangement, which is hereinafter referred to as an auxiliary control switch, is generally designated ACS, comprises individual switches 2M! through 2M4 which are operated by a circular cam 20 having a single projection thereon. The contacts of switches 2Ml-2M4 are normally closed except when operated by the cam 20, and these respective switches correspond to the correspondingly numbered switches of the respective stations Sl-S4 as identified by the last digit of the respective reference characters. Thus, for example, switches S13, S23, S43 and 2M3 are corresponding switches. Switch S33 is omitted since it is the master switch on station S3. Similarly, switches SI I, S22 and SM are the master switches of the corresponding switch stations Si, S2 and S4. These last named switches are each connected in series with auxiliary control switch 2MA. Switch ZMA, which also is normally closed, represents the position in which the selector switch SS is to be stopped for the purpose of connecting a given transducer with all of the other transducers of the system. This will be more fully described hereinafter.

As the various switches above considered are identified on the respective switch stations, the 'last'digit of the reference character indicates the particular station with which that particular switch is related. For instance, referring to the switch SI I, the last digit 1 indicates that such "switch'is in station I, and by further examination, with regard to the switch Sl3, the last digit '3 indicates that by depressing this switch the *transducer Tl may be connected with the trans- "ducer T3.

In the system herein illustrated the switch which is numbered in accordance with the number of the switch station in which it is located "is utilized to connect the transducer of that sta- -tion with all of the other transducers, by the 'control afforded through the contact ZMA of the auxiliary control switch ACS, thereby controlling the motor 2M in such a, way as to position the selector switch SS to establish connection of the remaining transducers. For example, by closing switch SH transducers T2 through T4 will be connected with the transducer Tl. In a similar manner on station S2 the push button switch S22 is connected with the contacts 2MA to effect connection of the transducer T2 with all other transducers Ti, T3 and T4, while either the switches S33, and S44 of the stations S3 and S4,

respectively, function in a similar capacity to connect the corresponding transducers with all the other transducers of the system.

In accomplishing this function the contacts H0, 220, 33c, and 440, respectively, of the switches SI I, S22, S33and S44 are connected to one con- .tact" of the switch 2MA, the other contact of which switch 2MA is connected in common with all of the corresponding contacts of the switches 2M! through 2M4 withone terminal of the motor 2M. The other terminal of motor 2M is connected to the conductor 2. As in the case of the set of switches which control motor IM, each of the switches Sll-SM now being considered in the respective stations S|-S4 is supplied with power from the conductor I through each of centrally located contacts thereof (such as the contact l Ib'of switch SH of station SI). The remaining switches of each of the stations Sl--S4 are utilized as earlier mentioned, to connect the transducer of that particular station with a correspondingly numbered transducer. This is accomplished by connecting these respective switches in series with the corresponding one of theswitches 2M| through 2M4.

-For example, 'the'contact I20 of the switch Sl2 isconnected in parallel with the contacts 320 and 420 of the switches S32 and S42, respectively, all of these contacts being connected to the remaining contact of the switch 2M2 of the auxiliary control switch. Hence, for example, upon the operation of puush button Sl2, a circuit is completed from conductor l to the power supply contact l2b, to the contact [20 of the switch Sl2,

to the contacts 2M2. From the common terminal of-these contacts, the circuit continues through "the motor 2M to the conductor 2 which completes the energizing circuit for the motor. Operation of the motor continues the rotation of the cam 20, until the cam projection opens the contacts 2M2, at which time the motor circuit is broken and the motor 2M is stopped.

*As illustrated, the motor 2M drives the selector switch SS as well as the auxiliary control .switch ACS. The selector switch SS is comprised of two separate switch sections, one of which'includes the separate contacts SSI through SS4, and the other of which includes an incomplate annular or arcuate contacti25, havinga projection 26 thereon forengagi-ng a stationary contact designated SSA. This stationary contact is electrically connectedto the movable switch element 21, both elements being supplied with power through a circuit including conductor; 21A, which willbe describedhereinafter; By means of parallel contacts which engage the 'arcuate contact 25, each of the contacts SSI through SS4 is connected therewith'fiuThe movable switch opening 25a in arcuate contact. 25 straddles the stationary contact associated therewith corresponding to contact SS3. Thus this contact is effectively disconnected from the 'arcuate contact 25. Similarly, when the cam 20 occupies any of the three remaining positions in which contacts SSI, SS2, andSS4 are engaged, opening 25a straddles the corresponding contact associated therewith and" therefore the arcuate contact is effectively disconnected from the circuitin each of the four single. stationnpositions of the cam 20. In the all station position of cam 20 switch'ZMA is opened on switch ACS; Movable contact' 2'lnow lies between contactsSSl and SS4'and projection 26 engages contact SSA connecting the arcuate contact to circuitQTA.

In this intermediate angular position of cam 20 the angular position of the arcuate contactis suchthat all four stationarycontacts associated therewith are engaged thereby to thus conn'ectall of thecontacts SSI through SS4 to conductor The various contacts SSlthrough SS4 of the selector switch SS are severally connected with certain corresponding contacts of switches Cl through C4 of the master switch u'nit MSS: The

contacts of each master switch unit (II- 04mmprise a'transfer contact assembly having a normally closed back contact and a normally open front contact. For example, the contact SSI is connected with one of the two back-contacts of the switch CI. The contact SS2=is "connected with one of the two backcontacts of 'the switch C2. The contact SS3'is connected with one of the two back contacts of the switch C3, and

the contact SS4 is connected with one of the two back contacts of the switch 04. The other back contact of each switch CIC4 is connected to the corresponding' front' contact, and these commonly connected contacts are respectively connected to thecorresponding transducers Tl-T l. For example, transducer TI is connected' with the commonIront-back contacts of the contact assembly Cl, and the transducer'T2 is connected with the'common front-back contacts of switch G2, etc.

It will be understood that each switch C1-C4 includes a pair of front contactsand a pair of back contactsand that'one front 'contact'and one back contact of each of said'switc hes are connected together, and as 'thus electrically paired are connected to the transducers TI to T4, respectively. As already noted, the back contacts of the switches C|-C4 which are not connected in common to the respective transducers TI-T4 are connected severally to the contacts SSI-SSQ, respectively, of the selector switch SS. The front contacts of the switches CIC4 which are not connected in common to the respective transducers T|-T4 are connected in common to the conductor CA leading to a reversing switch of the double-pole, double-throw type actuated by a relay R.

The circuit designated 21A, which energizes the movable element 21 and the stationary contact SSA of the selector switch SS, is also connected to the double-pole, double-throw reversing switch, and the circuits CA and 21A are connected together through an amplifier generally designated A, having the input and-output circuits designated I and 0, respectively, which are also connected to the reversing switch.

The reversing switch is shown in its normal or deenergized position. This switch includes two contact arms RI and R2, each arranged with two sets of transfer contacts. The back contacts of each set of transfer contacts are normally closed as shown, and, upon energization of the coil of the relay R, these contacts are opened and the front contacts thereof are closed. In the illustrated position of the reversing switch, the conductor CA is connected through the back contacts of the transfer contact assembly R2 to the output circuit of the amplifier, and the conductor 21A is connected through the back contacts to the transfer contact assembly RI to the input circuit I of the amplifier. These connections as will be hereinafter described connect the transducer at the station initiating a call with the output 0 of the amplifier and connect the called station or stations to the input of the amplifier. Thus to transmit a message from the calling to the called station the relay R must be operated from the calling station. Suitable switching means yet to be described is provided for this purpose at each station. While this mode of operation may be preferred for one application,-in other applications the reverse may prove more convenient in which case the conductor CA will normally be connected to the input of the amplifier A and the conductor 21A connected to the output. This will connect the calling station to the input I and the called station to the output 0. This; in practice, is ac- N complished by simply reversing the circuits I and 0 from that indicated. Switching means at the respective stations will again be provided to control relay R.

Assuming now that it is desired to connect the transducer 'II with the transducers T3, the push button switch assembly SI3 of station SI is depressed, connecting the contacts ISA and I30 with the energizing contact l3b. A circuit is therefore completed for energizing the motor IM which is traceable from the supply conductor I to contact I3b, to contact I3a, to the motor control contacts of switch IMI. Assuming for the moment that the contacts of switch IMI are closed, the motor-energizing circuit is completed through these contacts and the motor IM to the conductor 2. The motor is therefore operated until the projection II on cam I0 opens the switch IMI, at which time the motor circuit is interrupted and the motor stops. If the cam should be positioned as illustrated in the drawing at the time switch SI3 is closed, the motor IM is not energized, nor need it be.

A circuit for operating the motor 2M is also established through switch SI3 from supply conductor i to energizing contact lab, to conthe motor 2M to the supply conductor 2, thereby energizing such motor, and rotating the cam 20 until the contacts of switch 2M3 were opened and the motor ale-energized. In view of the proper indexing and the common rotation of the movable switch element 21 with respect to the cam 25, such switch element engages the contact SS3 of the selector switch SS when the motor 2M stops, and thereby completesa-circuit connecting the transducer Ti with the transducer T3. This circuit extends fromthe transducer TI through the conductor TIA to the commonly connected front and back contacts of the transfer switch Ci. The closing the pushiutton switch Sis having moved the cam I0 into the position shown in the drawing, the front contacts of the transfer contact assembly CI are closed and a circuit is established through these front contacts to the conductor CA connected thereto. From the conductor CA the circuit is connected to the output circuit 0 of the amplifier A through the hack contacts of the transswitch or contact assembly RE. From the output circuit 1 of the amplifier the circuit continues through the closed back contacts of the transferswitch or contact assembly RI to the conductor 213A, which is engaged by rotary arm r 27 to the contactSSE of the selector switch SS.

contact SS3 the circuit extends through the closed back contacts of the transfer contact assembly or switch C3 of master switch MSS, the commonly connected front and back contacts of which are connected to the transducer Thus, by the provision of the individual master and auxiliary selector switch assemblies MSS and ACS, the manipulation of the contact S13 automatically and quickly. interconnects the selected transducers Ti and T3. In this circuit connection, the transducer Tl is connected to the output circuit of the amplifier A and the transducer T3 is connected to the input circuit I of the amplifier. This circuit connection together with a selective switching control. for the relay R, (at each station) provides means whereby the operator at station SI may convey a message through the transducer TI to the transducer T3 without any necessity of the party at the transducer T3 taking any action.

The selective switching control at station 'S is a push button operated talk-listen switch designated SiT, provided to control the energization of the relay R. Depression of the push button sw' ch SiT energizes the coil of the relay R in a circuit which is traceable from the supply conductor I through the closed contactsof push button switch siT to the conductor TC, which is connected with the coil of relay R, and the circuit is completed through the coil-of relay to the supply conductor 2. This relay therefore picks up and closes the front contacts of the respective transfer contacts R! and R2, connecting the circuit CA with the input circuit I and the circuit 27A with the output circuit 0, which operation, it will be appreciated, reverses the connection of the transducers TI and T3 to the amplifier A, making it possible for the party at station SI to converse with party at station S3.

All of the remaining switch stations are provided with correspondin talk-listen .push' but-v tons which are designated SZT, S3T.:and-S4T, respectively. Each of these are connected to the conductor TC and are therefore in parallel with. one another and in series with the coilofthe relay Rf Hence, operation of anyone of these push buttons will energize the relay, thus affording selective control of the reversing switch fromany one of the four stations illustrated.

.--Advantageously, I. provide means for visually indicating the establishment of the circuits.be-'v tween any of the selected transducers vTl-T l upon'operation of any selected push button, and, also forindicating whether or not the system isbusy. Such indicating means may be of any suitable form and in the illustrated embodiment; lightsare utilized to indicate these conditions.

-More particularly, each station. is provided with a busy light, respectively, designated .BLl, BL2, BL3 and BLA, and each station is provided with. a pilot light which .indicatesthe establishmentof thedesired circuit. The pilot lights are..designated .PLl, vPLZZ, PL3. and PM, respec-,- tively. The control means for the busy light of each transducer is in the form of the-switch, which again may be a push button switch, but preferably. a switch which when closed will re-, main closed. These switches. are respectively designated SIL, SZL, S3L and S4L. ,The busy lights BL! through .BL4 are, connected in parallel with the

conductors

2a and 2b, and any one of the switches SIL through S411; is adapted, whenclosed, to connect the conductor 2bto the supply conductor 1, 5 Since the; conductor 2c, is connected to the .supply conductor 2, it willbe appreciated that .the closin c,f,,,,any -0ne of switches SIL through S4L establishes an energizing circuit for-allofthe busy lights across the supply conductors I, and 2. Thus, the lights being on atthe various stations indicate that the ,systemis presently in use. The pilot lights PL! through PM are so connected into the system that they are illuminated only at the sta tion at which the operation is initiated, inform: ing that part, when-the light is illuminated, that the desired circuit is completed. Hence-return ing to the. illustration wherein. the push button sltjis operated, as above described, the operator also closes the switch SlL,illuminating all of the bush lights ELI-BM, and at the same time establishin a partial connection for energizing the pilot light PLI. j f L The pilot lights are controlled bytheswitches L| "through L4 of the master selector switch MSS. These pilot flight switches are v.:severally located on the individual contact stacks of the master selector switch, and are therefore selectively operated with the respective switch stacks Qne contact of each switchLl- -L4 is connected to the supply conductori, and the other contact iof each of the light control switches. is connected in series withv the correspending pilot light (PLI PL4) and with the corresponding switch S1 L-SJL) Thus. the pressing of the push button sis and .thefclosi'ng of switch 4 S IL- is effective through I the operation cream. [0 to' move .theISwitchQstackTIIMI, ol and LI' into the position shown; which, in addition to interconnecting transducers TI and T3fas" already described; completes w en-elegai'rfg'circuit for the pilot light PLI of station Sl', said circuit extending from supply conductor 1 through switch SIL, through pilot light PL! and through the switch Lltosupply conductor-"2'.

Whileth'e light system is desirablefor= the 7 tratedI- At the same time a circuit for energizing' the motor 2M is completed from. supply conductor 'l through the contacts Ilb, lie and conductor=C to the iunction point JA, and thence through the contacts'of switch ZMA 'of the auxiliary control switch ACS and through themotor' -2M to supply conductor 2. Motor 2M therefore rotates cam 29 until the contacts ZMA: are opened and the operation of the mo-' ton interrupted. 5 B a -Withthe cam 20 and switch elements thus positioned, the rotary switch arm 21 is located between'the contacts SSl and SS4 of the selector switch! However, the projection 26 on the annular contact'25, which is electrically united to all of the contacts SSI through SS4,

at this time engages the stationary contact SSA, wherefore all of the terminals SSI through SS4 are connected with the back contacts of the transferswitches C2, C3 and C4 of the master selector switch MSS, while the switch CI stands removed from its backcontacts. The switches C2, C3 and 04, as thus closed across their back contacts, complete the circuits to the respective transducers T2, T3 and T4. While the back contacts ofthe switch Cl stand'open, as shown, the frontcontacts of this switch are closed, thereby connecting transducer TI to transducers T2, T3 andT4, the connection from the closed front contacts of switch CI of transducer Tl extendingthrough line CA, switch R2, amplifier A, switch-Rl, line21A, contact SSA, engaged byprojection 26 onring 25, and the conductors leading from said ring through the closed back contacts of switches C2, C3 and C4 to-thesaid transducers T2, T3 and T4. V

The ma'nipu1ation of the talk-listen switch SIT at station SI provides reversible communication between station SI and all of stations 82, S3 and S4. As inthe case wherein transducer Tl was connected with the transducer T3, the transducer TI is again connected to the output circuitof the amplifier A, while-the remaining transducers are-connected'to the input circuit thereofm' Although the amplifier circuit will normally be reversed by operation of the switch'Sl T at station SI, this circuit may also be reversed byoperation of any of the parallel connected switches S2T, S3T and S4T in the remaining switch stations- 5 -While the operation 0f the system'has been described'part by part with the development ofthe descriptionof the various components, a better understanding of the invention may be had from'a brief resume of the operation of the system asa whole. For convenience in this description, it will again beassumed that the transducer TFis-desired to be connected with the transducer T3. 111' operating the-system the operator at station 'Sl first depresses the light switch SIL to illuminate the busy lights: BLI through BL l. Thereafter the push button SI 3 is depressed and held down for an interval slightly longer than-that required to illuminate the pilot light PLI. With the depression of push. button SIS, the motor IM operates until the contacts IMI. of the master selector switch MSS are opened, which also opens the back contacts of the transfer switch Cl and closes the front contacts thereof, and at the same time closes the contacts Ll, which effects the illumination of the pilot light PLI. The clos ing of the switch Cl connects the transducer Tl through the then closed front contacts of the transfer contact switch CI to the conductor CA which is connected to the output circuit of the amplifier A. The energizing circuit closed from supply line I through contacts I32) and I30 to the contacts 2M3 of the auxiliary control switch ACS energizes the motor 2M, which stops when the cam 20 opens the contacts 2M3. In this position of the cam the rotary switch arm 21 engages contact SS3, and thereby completes an energizing circuit leading from the input circuit I of the amplifier A, relay switch R1, line 21A andarm 21 to the closed back contacts of the transfer, switch C3, and thence to the transducer T3, completing the desired circuit between the two transducers TI and T3. I

From the foregoing it will be appreciated that any one of the transducers TlT4 may be connected with any one of the remaining transducers by simply manipulating a selected push button on the corresponding station to effect the desired connection. Likewise any one transducer may be connected to all of the remaining transducers by operating the proper push button on that particular station.

It will be appreciated that the equipment at the respective stations Sl--S4 is both simple and inexpensive, including merely a transducer which may comprise a permanent magnet speaker commonly used for this purpose, and a pushbutton assembly having a push-button for each station of the system, together with a talk-listen push-button, and an indicating light switch, ifdesired. Elements such as these are inexpensive and are easily and conveniently arranged in an attractive and compact unit.

The remaining components of the system: are also relatively simple and easily manufactured. These components, for example the master switch MMS, the auxiliary selector switch SS, the auxiliary control switch ACS, and the electric motors IM and 2M therefor may be conveniently assembled .on a single base. The entire arrangement is small in dimension, which may, together with the single amplifier A be disposed at a convenient point in the system, where the various stations may be. easily wired and available for service.

With these few components it should be noted each station of the system is a master station, where a person may converse at will with any one or with all of the otherstations, without the need for personnel at any of the other stations to take part in the establishment of the circuits, or in the operation of the system for two-way communication. Thus, it will be appreciated that in addition to the simplicity of the equipment, the equipment is highly flexible and at the-same time, very easily operated.

While cam-operated switches have been herein indicated for performing the various switching functions, it will be appreciated by those skilled in the art that relay circuits may be readily substituted, therefor. The present, arrangement in many instances will be preferred, since the cost of equipment of the type herein 12 shown is a great deal less than that of relay equipment. Furthermore, the unit assembly of the switches is relatively compact.

The indicating light system may be elaborated, if desired, by connecting the lights respectively in a circuit including in series therein, in addition to the respective switches LI through L4, a corresponding set of switches on the auxiliary control switch ACS, each of which would be connected in series with its corresponding switch Ll through L4, the circuit being completed to the conductor 2 in exactly the same manner as the present circuit for the switches LI and L4. With such an arrangement all of the series switches would of necessity be closed prior to the time the pilot lights of the respective stations would be illuminated.

While a preferred embodiment of this invention has been illustrated and described, it will be appreciated by those skilled in the art that numerous changes in the circuit and its components, and in the arrangement of these circuit components, may be made Without departing from the spirit of the invention defined in the appended claims.

I claim:

1. An interccmmunication system comprising a switching network for connecting together a plurality of electrical transducers comprising in combination, a switch station for each transducer, each switch station compring a switch for each station; each switch having a first normally open contact and a second normally open contact, circuit means connecting said first contacts of each switch station in parallel, circuit means connecting the corresponding second contacts of the separate switch stations in parallel, a master switch unit for each station; an auxiliary switch unit for each station; master switch control circuit means connecting each master switch unit with the paralleled first contacts of the corresponding switch station, auxiliary switch control circuit means connecting each auxiliary switch unit with the corresponding paralleled second contacts, circuit means connecting each transducer with the corresponding master switch unit, and circuit means connecting the corresponding auxiliary switch units and master switch units.

An intercommunication system comprising a switching network for connecting together a. plurality of electrical transducers comprising in combination a switch station for each transducer, each switch station comprising a switch for each station; each switch having a first normally open contact and a second normally open contact, each switch representing at least one station other than the station at which his located, circuit means connecting said first contacts of each switch station in parallel, circuit means connecting the corresponding second contacts of the several switch stations in parallel, and circuit means responsive to operation of any particular switch of a given station for connecting the transducer of said given station to the transducer of the station represented by said'particular switch. I

3. An intercommunication system comprising a plurality of transducers, a-master switch unit for'each transducer, an auxiliary switch unit for each transducer, circuit means connecting each transducer to the corresponding master -switch unit, circuit means connected in common with all the master switch units and all the auxiliary switch units, circuit means for individually connecting the master switch units to the corresponding ,auxiliary switch units, and circuit cgsergeceir 13. means: for simultaneously actuating a selected master switch unit and a selected auxiliary switch unit.

4. Apparatus as said circuit means connected in common with all the master and auxiliar switch units comprises an amplifier having aninput and an output circuit connected in series witheach of the master-switch units and each of the auxiliary switch units.

' 5. Apparatus as set forth in claim Binwhich said :circuit means connected in common with.

all. .the master and auxiliary switch units comprises an amplifier having an input and an output circuit connected in series with each of the master switch units and each of the auxiliary switch units, a reversing switch for reversing the connection of said input circuit and output circuit; and a separate switch for each transducer for actuating'said reversing switch. e .1

intercommunication system comprisin aplurality of transducers, a master switch unit for each transduceneach master switch unit having. a pair of normally open contacts and a pair or normally closed contacts, one normally open contact'and'one normally closed. contact'of each of said-pairs of contacts in each master switch unit having a common terminal, circuit means connecting each transducer to said commonterminal of the. corresponding master switch unit,

an auxiliary switch having a pair of contacts, electrical conductor means connecting all of the other normally open contacts of the several master-switch units with one of said pair of contacts of-said auxiliary switch, circuit means connectingall of the other normallyclosed contacts of theiseveral master switch units withthe other of circuit, said input circuit being connected with all said other terminals of said normally open contacts and said output circuit being connected to said one contact of said pair of contacts of said auxiliary switch, and a reversing switch connected with said input circuit and said output 'cir cuit for reversing-the. connection of said 'inpu and output circuits. v

, 9,,A'I'i intercommunication system comprising a plurality'of transducers, amaster switch unit foreach transducer, each master switch unitincluding a pair of normally open contacts and a pair of normally closed contacts, one normally open and one normally closed contact of each pair "of said contacts having a common terminal, an auxiliary control switch assembly including an auxiliary switch for each transducer, each auxiliary switch having a pair of contacts for each transducer, each auxiliary switch having one contact of each pair of contacts connected in common, a selector switch connected to operate in synchronism with said auxiliary control switch assembly, circuit means connecting the transducers respectively to said common terminals of said master switch units, control circuit means connecting each of the other contacts of said auxiliary switches respectively to the other of said normally closed contacts of said master switch set forthin claim 3, in which 3, in which 14 IT unit's, 'circui't means connecting the other contactof said selector switch with each of said othercontacts of said auxiliary switches of the auxiliary control switch assembly, and circuit means for simultaneously operating a selectedmaster switch unit and an auxiliary switch of said auxiliary control switch assembly. I

10. Apparatus as set forth in claim 9, in which said control circuit means includes an amplifier. 11.- Apparatus as set forth in claim 9, in which said control means includes an amplifier having an "input circuit and an output circuit, and a reversing switch normally connecting said input circuit to the other contactsof said normally open contacts of said master switch 'units', and means electrically connecting'said output circuit to the-common-connected contacts of said auxiliary switches and to a contact of said selector switch. 1

-12.'Apparatus as set forth in claim 9, a cam foractuating the master switch units, a motor for driving said eam, switch means on each master switch unit for controlling said motor, and con trolcircuit means selectively connecting each of said switch means and said motor in series.

'13. A-pilot-light circuit for an intercommunication system comprising the combination of a plurality of transducers, a masterselector switch havinga plurality of master switch units severally connected tosaid transducers, anauxiliary control switch assembly having an auxiliary switch unit for each transducer connected with a corresponding master switch unit, a switch station for-each transducer including a switch for eachtransducer, all the switches of each switch station being connected with the corresponding master switch unit and the corresponding switches of each .station being connected with the corresponding auxiliary switch units, a pilot light for "bination of a plurality of transducers, a motor operated master switch unit for each transducer;

a motor operated auxiliary switch unit for each transducer, circuitmeans connecting the corresponding. auxiliary switch and master switch units, circuit means connecting eachtransducer With the corresponding master switch unit, and switching means for each transducer for controlling the motor-operated master switch unit for controlling the motor operated auxiliary switch unit.

16. In an intercommunication system, the combination. of aplurality of speaker-microphone stations each having individual switch units corresponding in number to the number of said stations, a master switch assembly comprising a plurality of master switch units corresponding in number of the number of said stations, an auxiliary switch unit comprising a plurality of auxiliary switch units corresponding in number to the number of said stations, circuit means responsive to operation of any one switch on one of said stations for operating the corresponding master switch unit, circuit means responsive to operation of any one of the corresponding switches on the different stations for operating the corresponding auxiliary switch unit, circuit means connecting each speakermicrophone unit with the corresponding master switch unit, and circuit means connecting each auxiliary switch unit with the corresponding master switch unit.

1'7. In an intercommunication system for selectively connecting together a plurality of electrical devices, the combination of a switch station for each device having individual switch units corresponding in number to the number of devices, a master switch assembly having a plurality of master switch units corresponding in number to the number of switch stations, an auxiliary switch assembly having a plurality of auxiliary switch units corresponding in number to the number of said switch stations, circuit means responsive to operation of any one switch of one of said stations for operating the corresponding master switch unit, circuit means responsive to operation of any one of, the corresponding switches of the different switch stations for operating the corresponding auxiliary switch unit, circuit means connecting each electrical device with the corresponding master switch unit, and circuit means connecting each auxiliary switch unit with the corresponding master switch unit.

18. In an intercommunication system for selectively connecting together a plurality of electrical transducers, the combination of a switch station for each transducer having an individual switch unit for each transducer, a master switch assembly having a master switch for each transducer, each master switch unit having a normally open contact and a normally closed contact, an auxiliary switch assembly having an auxiliary switch unit for each transducer, a common circuit for each normally open contact of the jaster switch units, a common circuit for the auxiliary switch units, circuit means connecting said common circuits together, circuit means connecting each transducer to the corresponding normally open and normally closed contacts of the master switch units, circuit means connecting each auxiliary switch unit with the corresponding normally closed contact of each master switch unit, circuit means connected With each switch station and responsive to operation of any one switch of one of. said stations for operating the corresponding master switch unit, and circuit means responsive to operation of any one of the corresponding switches of the differ-- ent switch stations for operatin the correspond-- ing auxiliary switch unit.

19. In an intercommunication system for selectively connecting together a plurality of electrical transducers, the combination of a switch station for each transducer, each switch station comprisin one switch for each station, each switch having; pair of normally open contacts, a master switch unit for each switch station, an auxiliary switch unit for each station, circuit means connecting the corresponding contacts on the several switch stations in parallel, circuit means connectin the. remaining. contact of each switch in parallel with corresponding remaining contacts of the switches on theother switch stations, control circuit means for each master switch unit connected with the paralleled contacts of corresponding switch stations, control circuit means: for each auxiliary switch unit connected with the corresponding paralleled remaining contacts of the separate-switch units, circuit means-connecting the corresponding master switch units and auxiliary switch units together, and circuit means connecting each transducer with the corresponding master switch. unit.

20.v In an intercommunication system, the combination of a, plurality of stations each including a speaker-microphone and. a push-button control having push-buttons corresponding in. number to the number of stations, a pair of contacts for each push-button, a master selector switch including, a switch stack. for each station, each switch stack: having, a normally closed con tactv and a normally open contact, an auxiliary selector. switch including a switchstackfor each. station, an amplifier having an. inputcircuitand.

an output circuit, means. connecting each speaker-microphone with the normally open contact of the corresponding master switch stack, circuit means connecting each normally open contact of said master switch with oneof the circuits of said amplifier, circuit means connecting each switch stack of said auxiliary switch with the other circuit of said amplifier, circuit means.

connecting each switch stack of said auxiliary switch in series with the corresponding normallyclosed' contactv of said. master switch. and with. the correspondin speaker-microphone, actuate ing means for the master switch. for selectively actuating the switch assemblies of the master switch in response to operation of any one. push button on the respective: push-button controls. and second actuating means for selectively actuating any one switch stackof said. auxiliary switch in response to operation of. correspond-- ing push-buttons of. the "respective push-button controls.

FRANK PEDATELLA.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED- STATES. PATENTS Number Name Date 2,162,369 Campbell June 1.3', 1939 2,162,370 Campbell June13, 1939'. 224:9,4-56 Campbell Apr. I8, 1941 2,269,144 Campbell Jan. 6; 1942 2,347,079 Campbell. Apr. 18;, 1944. 2,496,159 'Hagens' Jan. 31, i950