US2241663A - System of communication - Google Patents

Description

May 13, 1941. LA MAR E. HAYSLETT Erm. 2,241,663

SYSTEM oF COMMUNICATION Filed Sept. 3, 1940 3 Sheets-Sheet l May 13, 1941. LA MAR E. HAYSLETT ET Al. 2,241,663

SYSTEM OF COMMUNI CAT ION 5 Sheets-Sheet 2 Filed Sept. 5, 1940 sneer sr van:

. HNHK E BY FAW/V05 /Z M May 13, 1941. LA MAR E. HAYSLETT E1- Al. 2,241,663

SYSTEM OF COMMUNICATION Filed Sept. 5, 1940 3 Sheets-Sheet I5 sussckwsk /IOVI PI. a

Patented .May 13, 1941 SYSTEM F COMMUNICATION Ll Mal' E. Schmidt.

Hayllett, Kenmore, and Francis M. North Tonawanda., N.

Y., asslgnors to The Rudolph Wurlitzer Company, Cincinnati,

Ohio, a corporationy Applieeuen september s, 1940, seiei No. 355,140

(ci. ris-s) 7Clalms.

This invention relates to a system of communication particularly adapted to the dispensing of music or other form of audible entertainment from a central station to a plurality of subscribers stations.

One object of the invention is to increase the interest in entertainment of this type in restaurants and other establishments where coin-operated phonographs are generally installed.l This object is attained by the provision of means by which a person desiring to hear a given selection after depositing a coin may make his selection orally by speaking directly to the phonograph in response to an inquiry from a central station operator transmitted through the speaker of the phonograph. This arrangement introduces a novel personal element in the operation of mechanism of this kind which stimulates the interest of prospective customers and increases the income from such apparatus.

Another object of the invention is to provide a central station system for dispensing entertainment which requires a minimum of Wiring connection between the central station and subscribers stations. In the preferred form of the apparatus described herein a single two-wire metallic circuit is used between the central station and each subscribers station. Return talk and all necessary signals are transmitted by a grounded simplex or half-phantom circuit connected to the two-wire circuit without interfering in any way with the transmission of programs and voice on the two-wire circuit.

Another object of the invention is to provide suitable apparatus by means of which ordinary mechanical selection of programs may be accomplished during hours of slack business when it be lm mediately notified of the receipt of a coin whether or not all selections have been delivered for coins previously received.

In the preferred form ofthe invention described herein, there is provided a central station having a plurality of phonograph mechanisms each provided with a pickup, turntable and associated operating apparatus and each is not advantageous to have a central operator` normally connected through suitable amplifiers to a speaker at one of a number of subscribers stations. The central station is also provided with av coin registering device for each of the subscribers stations and said devices are normally connected to and operated by coin receivers at the subscribers stations. The central station is also provided with a transmitter and receiver which may be any suitable type employed in telephone transmission or may be of the microphone and speaker type as desired. Each subscribers station is provided with a transmitter preferably of the microphone type and preferably installed in the same cabinet as the subscribers speaker. At the central station, keying means are used for selectively connecting the central transmitter to the speaker at any one of the subscribers stations and for connecting the corresponding subscribers transmitter to the central station receiver. At each subscribers station there is provided in addition a local record changing phonograph mechanism equipped with the usual magazine switch and with a change-over switch adapted alternatively.

to connect the speaker and usual phono-amplifier to the local phonograph mechanism or to the central station and to connect the coin receiver to the magazine switch or tothe central station.`

Otherobjects and features of the invention will be understood from the accompanying drawvings and the following description and claims:

Fig. 1 is a diagrammatic elevational view showing a preferred arrangement of the central station. Fig. 2 is aperspective view of the central station operators control board. Fig. 3 is a perspective view of the upper portion of a phonograph cabinet used at a subscribers station, with parts arranged for the ordinary mechanical oper. ation. Fig. 4 is a similar view of the same cabinet with parts arranged for central station operation. Fig. 5 is a sectional view showing an arrangement of parts by which the mechanical selector keys of the cabinet shown in Figs. 3 and 4 r are made inaccessible when central station operation is in use. Fig. 6 is an elevational view partly in section showing a preferred form of coin register unit used with the central station control board of Fig. 2. Fig. 7 is a diagram of electrical connections at the central station. Fig.`8 is a diagram of electrical connections at one of the subscribers stations.

Referring now particularly to Fig. 1, in which there is illustrated a preferred arrangement of the central station, there is provided a table or Above the door 2I there is shelf I on which there is mounted a control board II shown in more detail in Fig. 2. On table I0 at each side of the control board II and on shelves I2 there are provided a plurality of phonograph mechanisms I3 each equipped with a turntable I4, a pickup I5 and the necessary' mechanism, not shown, for rotating the turntable. The phonograph mechanisms I3, herein shown as ten in number, are conveniently placed to be operated by an operator seated before the control board II. Each phonograph mechanism is provided with a checkoif switch I6, the purpose of which will be described hereinafter. A transmitter in the form of a microphone I1 is provided and may be mounted on a stand I8 placed connection with the electric circuits of which they form a part.

Referring now to Fig. 3, showing a form of phonograph cabinet employed at the subscribers station, said cabinet is provided with the usual front door 2I having a. glass window 22 therein through which a record magazine 23 and record changing mechanism of any well known form are visible. Beneath the door 2I there is provided a plurality of selector keys 24 adapted to control the selection of records contained in the magazine 23 in accordance with similarly numbered program cards 25 which are visible through the window 22. The cabinet also includes three coin receivers 26 of any well known type adapted to receive coins of different denominations. provided a screen 21a behind which there is mounted a subscribers microphone 21. l

Referring now to Fig. 4, the same phonograph cabinet is shown arranged for central station operation. In

24 are covered by a panel 28 carrying the legend this arrangement the selector keys Select by Voice. Said panel is arranged as best shown in Fig. 5 and is opening the door 2I, then closing and locking said door. At the same time, a selection list 29 printed on heavy cardboard or other suitable material and bearing the legend Select by Voice is placed in a suitable retainer behind the glass window 22. Said selection list effectively hides the selection cards 25 and the mechanical record changing mechanism from the view of prospective customers. The electrical connections by which the changeover from mechanical to central station operation is performed are described hereinafter.

Central station electrical apparatus placed in position by first inserting the panel and power for'. operating the central station is received from any suitable source on power mains 30 and preferably is the volt alternating current. One of said power mains has connected therein a cutout switch 3I and the other carries the usual overload fuse protection 32. A transformer 33 has its primary winding connected to the mains 30 and is provided with a secondary winding 34 providing alternating current at a low voltage suitable for usual commercial 110 heating the cathodes of the vacuum tubes used in the various amplifiers at the central station. The connection of the cathode heaters may be conventional and for that reason is not shown in the drawings. Direct current is supplied to a pair of distributory conductors 36a and 36h from a secondary winding 31 of transformer 33 con nected through a conventional rectifier unit 38. Said distributory conductors are grounded through resistors 39 and 40 respectively. Resistor 39 is proportioned to maintain the conductor 36a at a suitable positive potential to supply plate current for the several amplifier units and to operate certain direct current relays. Resistor 40 is proportioned to maintain conductor 36h at a negative potential of a few volts.

Other central station electrical apparatus .includes a phonograph preamplifier 4I associated with each of the phonograph pickups I5. Two of said preampliers are shown in detail in Fig. 'I and the remainder may be similar. A coin signal device 42 for each subscribers station is also located at the central station and two of said devices are shown diagrammatically in Fig. 7. The central station transmitter I1 is equipped with a preamplifier 43 and the central station speaker I9 is equipped with an amplifier 44.

subscribers station electrical apparatus Referring now to Fig. 8, in which there is diagrammatically shown the electrical apparatus of one subscribers station, power. for operating the station is supplied on a pair of power mains 45 and 46 connected to any suitable source, preferably 110 volt alternating current. One of said power mains is provided with a cutout switch 41 and the other carries a protecting fuse 48. A changeover switch 49, herein shown as a twoposition multi-polar knife switch, is provided for the purpose of changeover from central station operation to local mechanical selection. When thrown to the left in Fig. 8 for central station operation, said switch connects the power mains 45 and 46 to the primary winding of a transformer 50. Said transformer is equipped with a secondary winding 5I adapted to supply low voltage alternating current for heating the cathodes of vacuum tubes used in the local microphone preamplifier 52 associated with the local microphone 21. Said microphone is preferably located behind the screen 21a in the cabinet 20 as previously described. The transformer is provided with a secondary winding 54 connected to a rectifier tube 55 supplying direct current at a suitable potential above ground to a conductor 56.. Within the preamplifier 62 suitable plate voltages are secured by conventional connections to the conductor 56.

Other apparatus at the subscribers station shownv diagrammatically in Fig. 8 includes a phonograph mechanism indicated by name and provided with a plckip 51, a speaker 58, an amplifler for said speaker indicated PHONO AMP, a magazine switch indicated MS and a coin switch indicated COIN SW. All of said apparatus is preferably housed in the cabinet 20 and may be of any construction suitable for coin Wiring and operation The wiring connections shown in Figs. 7l and 8 may best be described in connection with a description of the operation of the apparatus.

Operation-local mechanical selection Power for operating the phonograph mechanism is supplied by direct connection to power main 5 and by connection to power main 46 through conductor 59 and the magazine switch MS. When the changeover switch 49v is thrown to the right in Fig, 8, the magazine switch is connected to conductors 60 and 6| leading to the coin switch and its operation is controlled by operation of the coin switch. At the same time, power for operating the phono-amplifier and speaker is supplied by direct connection to power main .45 and by connection to power main 46 through conductor 62, switch 49, conductor 63 and the magazine switch. The pickup 51 is connected to the phono-amplifier through switch 49 and conductor 64. These connections complete all circuits necessary for local operation of the phonograph. When switch 49 is thrown to ythe left, the pickup 51 is disconnected from the amplier, the coin switch is disconnected from the magazine switch and conductor 62 is directly connected to power main 46 for operation of lthe phono-amplifier and speaker 58 independently of Vthe magazine switch.

Phonograph transmission from central station 'Ihe output of each of the pickups I 5 at the central station is preamplied by its associated amplifier 4| and is impressed on the primary winding of an output .transformer 69. The secondary winding 10 of said transformer has its terminals connected to a pair of conductors 1| and 12 leading to the corresponding subscribers station. The volume of the output impressed on the conductors 1| and 12 is controlled by a variable resistor 13 operated by control knob 13a on -the central station control board (Fig. 2). At the subscribers station the conductors 1| and 12 are connected to the terminals of the primary winding 14 of an input transformer 15. The secondary winding 16 of said transformer has one terminal grounded and the other terminal connected through a series of resistance units 11, the changeover switch 49 and conductor 64 to the phono-amplifier and speaker. The function of the resistance units 11 ls to modify the output received from the transmission lines put transformer 1| and 12 to give it substantially the same characteristics as the output of the pickup 51.

By means of these connections, each of the phonograph units i3 at the central station is connected by a two-wire metallic circuit to the corresponding subscribers station and each may be manually operated by the central station operator to deliver a desired selection to the subscribers speaker.

VfIVhe output `oir'the central station -transmitter |1 iswamplifeddbyits preamplifier circuits 43 and 75 is impressed on the primary winding of an out 80. The secondary winding 8i of said transformer has one terminal connected through a switch operated by a key 82 to a bus line 84 and its opposite terminal connected to a bus line 85, Said bus lines may be selectively connected to the conductors 1| and 12 of any given subscribers station by operation of normally open switches controlled by push buttons' 86, one of said push buttons -being provided for each of the subscribers stations. buttons 86 are mechanically interlocked in a well known manner so as to be mutually exclusive. That is, each push button when pressed is latched in position to connect its associated subscribers station to the bus lines 84 and 85 andv automatically release Ito the normal position any of said push buttons which have been previously pressed. A push button 81 is provided for manually releasing all of the buttons 8B when it is desired that none of the subscribers stations be connected to the bus lines. The volume of the output is controlled by a variable resistor 88 operated by a knob 88a on ythe control board (Fig 2). A meter 89 mounted on the control board is connected across the bus lines 84 and to indicate the energy level of` the output to the subscribers station which may be connected to said bus lines.

By means of the connections just described, the amplied output of the central station transmitter may be impressed on the two-wire metallic circuit leading to any one of the subscribers stations by operation of the appropriate push button 86 and the talking key 82. Since the secondaries of transformers 69 and 80 are in parallel connection, the voice output may be superimposed on a musical program already in progress of transmission. By manipulation of the volume controls 13 and 88 the operator may adjust the combined output of the phonograph and voice units to the proper level for transmission over commercial telephone wires as indicated by the meter 89 and may reduce the volume of the phonograph output to make the voice clearly audible, if necessary. The operator is aided in making the latter adjustment by the fact that the subscribers transmitter 21 is sufficiently close to the subscribers speaker 58 so that the output of said speaker is fed back to the central station receiver through the return talk circuits now to be described.

Voice transmissiom-subscribers station to central station The output of the subscribers station transmitter 21 is amplified by its preamplifier circuits 52 and is fed to the primary winding of an output transformer 90, the secondary winding of which has one terminal connected to the midpoint of the Winding 14 of transformer 15 and the other terminal grounded through a condenser 9| having proper capacity for freely transmitting alternating currents of audible frequencies. At the central station the midpoint of winding 10 of each transformer 69 is connected to one terminal of the primary windtransformer 93, the opposite terminal of which is grounded. The connections just described will be recognized as a grounded simplex or half-phantom circuit in which alternating current energy induced in the secondary winding of transformer 90 is transmitted over conductors 1| and 12 in parallel, through windings 18 and 92 to ground and returns-through The push ground and condenser Si to transformer 90. By proper balance of the windings 14 and 10 the current now in conductors 1| and 12 may be made equal.. the two current components have equal and opposite effects on the winding and so do not interfere with transmission to the subscribers station.

@ne terminal oi the secondary winding of transformer @a is connected through a condenser and a normally open switch controlled by push button tt to a bus line 95 which is grounded through a resistor @d and a potentiometer 91. The opposite terminal is connected to ground through distributory conductor tito and resistance tu to complete a secondary circuit. The potentiometer @i is operated by a knob 91a (Fig. 2) to vicy-passk a variable portion of the energy in the secondary circuit to the amplier M for the central station transmitter I9. By thus varylng the total resistance of the circuit the current iiow and voltage may be controlled by the operator to keep the volumev level within the limits required for transmission over commercial telephone lines. The level of volume is indicated by a meter 98 connected across the potentiometer 91.

A resistor 99 may be shunted across the potentiometer 91 by operation of a normally open switch controlled by the talking key 82 and serves to reduce the output volume of speaker I9 when so connected. By this means the central station operator may have the beneiit of as large a volume from the speaker |9 as may be desired as long as the central station transmitter is not connected for transmission. When the later connection is made, the volume level of the speaker |9 is automatically reduced to prevent the sound from feeding back into the transmitter l1 and causing an undesirable blare in the subscribers speaker.

Signal transmission When the changeover switch 49 at any subscribers station is thrown to the left (Fig. 8), the conductors 60 and 6| leading to the coin switch are disconnected from the magazine switch MS and are connected respectively to the midpoint of transformer winding 14 through the secondary winding of transformer 90 and to one terminal of a secondary winding of transformer 50, the opposite terminal oiA which is grounded. By this means the operation of the coin switch impresses on the simplex transmission circuit to the central station a signal in the form of an alternating voltage having the frequency oi' the alternating current power supply. Said frequency is preferably 60 cycles per second.

At the central station the incoming low frequency coin signal is transmitted to the secondary circuit of transformer 93 in the same manner as the incoming voice signals but the coin signal is prevented from reaching the amplier M by a reactance unit |0| and condenser |02 connected in series across the input lines to said amplier and serving to lter out the lower fre-- quencies. A reactance |03 and condenser |04 connected in series across the secondary terminals of transformer 93 serve as a low pass lter to transmit the coin signal to a tube |05 havng suitable electrodes and connections for rectification and' amplication.

The amplifier cathode |06 of said tube is grounded and the amplier anode |01 ls connected to an electromagnetic relay |08, the oping Current POWQT mains .value the magnet posite terminal of which is connected to the positive direct current distributory conductor 36a. The amplifier grid |0557 is normally biased to cut ou by connection to conductor 36h. Each ltir-ne a coin signal fied current through cathode resistor |05R increases the grid potential to a point where sufficient current may flow to operate relay |08. By means of these connections each momentary closure of the coin switch at one of the subscribers stations momentarily actuates the corresponding relay 508 at the central station.

Each momentary actuation of the electromagnet i0@ momentarily closes a pair of normally open switches H2 and H3. The operation of switch i i2 completes a circuit from the alternat- 30 for operation of an electromagnetI ilfi. Said magnet forms part of a coin register device consisting of a ratchet wheel i l5 normally urged in the clockwise direction by a coil spring H6. Said ratchet Wheel is held in position by an escapement ||1 operated by an electromagnet ||8 and is moved against the action of spring IIB by means of a pawl ||9 operated by the magnet H4. The ratchet wheel ||5 carries a grounded contact member |20 adapted to engage a contact segment |2|. In the normal idle position of the apparatus when no coin signals have been received from the subscribers station, the contact member |20 is out of engagement with the contact segment |2| as shown in Fig. 7. Upon receipt of a coin having unit ||4 is momentarily actuated and operates the pawl ||9 to move the ratchet wheel ||5 to engage the contact members |20 and |2|. Successive actuations of the magnet ||4 by receipt of additional coins or by coins of more than unit value move the ratchet Wheelv I5 still farther in the counter-clockwise direction. The contact segment |2| is made suiiiciently long to maintain contact through any desired number of such actuations. The checkoi magnet ||8 is operated by the push button switch I6 previously mentioned which completes a circuit for said magnet from the alternating current power mains 30. The magnet ||8 operates the escapement ||1 to permit the spring IIB to move the ratchet wheel I5 one step in the clockwise direction. Obviously when the number of actuations of magnet ||8 equals the number of coin values which have been registered by the magnet ||4, the contact member |20 has returned to initial position and contact with the segment |2| is broken.

The engagement of contact members |20 .and |2| completes a. circuit for a pair of signal lamps |22 and |23, said circuit leading from a secondary Winding |24 of transformer 33, through a conductor |35 to said lamps and thence through said contact members to ground and to a grounded terminal of winding |24. The lamp |22 is located on the operators control board as shown in Fig. 2 and the lamp |23 is positioned behind said board as best seen in Fig. 6. The control board is provided with a. number of openings |34 behind each of which is positioned the coin register unit stations. IIn Fig. 6 the ratchet wheel ||5 of one of said units is indicated vand is mounted on an inclined shaft |35 carrying a transparent frustoconical member |36. Said member is positioned to be visible through the opening |34 and carries opaque figures |31, one of which is visible through said openings at each position of the ratchet wheel H5. The lamp |23 positioned is received,the flow of rectiv 42 of one of the subscribers within the frusto-conical member as shown in Fig. 6 increases the visibility of the numbers |31.

By means of the construction just described, the signal lamps |22 and |23 are lighted for a given subscribers station when a coin has been deposited at that station. Said lamps remain lighted until a corresponding number of selections have been checked oi by operation of the push buttons I6. The position of the ratchet wheel H and the indication of said position af- Iorded by the figures I3'I, visible throughthe opening |34, indicates to the central station operator how many selections are still to be 'delivered to that subscribers station.

The operation of the switch II3 each time the electromagnet |08 is actuated completes a circuit from the positive direct current supply line 36a through a resistor |38, an electromagnetic relay |39 and switch |03 -to ground. The relay |39 is of the type known as a stick relay,-that is, it is provided with a holding circuit which is completed when the relay is actuated and holds the relay in energized condition even though the original actuating circuit is broken. The holding circuit leads from said relay, through a switch |40, a conductor I4I and a normally closed switch |42 to ground. The switch |42 is opened by actuation ofthe push button 80 at -the same time that the normally open switches controlled by said push` button are closed. The switch |40 is closed to complete the holding circuit by the actuation of the magnet |39 and retains the magnet in the actuated condition after switch I I3 is opened until switch |42 has been opened.

The actuation of magnet |39 closes a switch |43 which completes a circuit from the alternating currentl supply line to a lamp I 44, the opposite terminal of which is grounded. Said lamp therefore is lighted as long as the relay |39 is energized. By means of this arrangement the lamp |44 is lighted when a coin has been deposited at the corresponding subscribers station. When the operator presses the key 86 to connect the central station receiver I9 to the transmitter at the subscribers station, the switch I 42 is opened, the relay |39 is deenergized and lamp |44 is extinguished. The lamp |44 thus performs a diiierent function than the lamps |22 and |23 since it indicates only that a coin has been deposited but` that no connection has yet been made for return talk from that particular subscribers station. If a number of coin values have been received at the subscribers station, the lamps |22 and |23 remain lighted until the corresponding number of selections have been delivered but the lamp |44 is extinguished as soon as the call from the subscribers station has been answered. If another coin is inserted before the lamps |22 and |23 are extinguished, the lamp |24 is again lighted to indicate the receipt of the additional coin and to notify the operator that the subscribers station must again be connected for return talk.

Rsum of operation station transmitter II to the subscribers speaker 58. The operator at the same time may operate the key 82 to complete the last named connection and to reduce automatically 'the volume level of the central station speaker I9. The operator then requests the customer to name his choice of music and the customer answers by speaking directly to the phonograph cabinet. Itis also possible at this time that a pleasant-voiced central station operator may persuade the customer to make an additional d eposit for more entertainment. When the customer has named the selection or selections he desires, the operator manually starts the corresponding phonograph mechanism I3 and at the same time checks orf one coin value by operating'the corresponding switch I6. When there is no occasion for conversation over the line, the operator will ordinarily release the key 82 to disconnect the central station transmitter I'I and will release all of the push buttons 86. However, the operator may at any time press one of the push buttons 86 and listen in on any of the subscribers'stations and may initiate conversations with customers at said stations if desired.

The invention has been described in one of its preferred forms, the details of which may be varied between wide limits without departing from the scope of the invention as deiined in the appended claims.

The invention claimed is:

, 1. In a communication system having a central station and a subscribers station, a phonograph reproducer mechanism, a coin register device, a telephone receiver, and a telephone transmitter located at said central station, a speaker, a transmitter and a coin receiving device at said subscribers station, a two-wire metallic electric circuit between said stations, said circuit connecting said reproducer mechanism and said speaker, keying means adapted to connect the central station transmitter in said circuit, electrical connections associated with said two-wire circuit at each station and forming therewith a grounded half-phantom circuit between said sta. tions, said coin register device and said coin receiving device being connected in said half-phantom circuit and said receiving device being adapted to actuate said register device through' said circuit upon receipt of a coin, and keying means adapted to connect the subscribers transmitter and the centralv station receiver through said half-phantom circuit.

2. The combination defined by claim 1 with the addition of a magazine phonograph mechanism at said subscribers station, a magazine switch connected to control operation thereof, and a cutover switch and associated wiring adapted to disconnect said speaker and coin receiving device from said two-wire circuit .and said half-phantom circuit respectively and to connect the same to said magazine phonograph mechanism and to said magazine switch respectively.

3. In a communication system having a cen- 'tral station and one or more subscribers stations, a plurality of phonograph reproducer mechanisms, a receiver and a telephone transmitter located at said central station, a speaker and a transmitter located at veach of said subscribers stations, electrical connections between said central station and each of said subscribers stations adapted to connect the speaker at each station to a corresponding reproducer mechanism, keying means associated with said electrical connections and adapted selectively to connect the central station receiver to any one of the subscrib Y ers transmitters, switching means adapted to connect the central station transmitter to the speaker at the subscribers station whose transmitter is so connected, an amplier operating the central station receiver, a volume control unit associated therewith, and switching means automatically operated with said iirst mentioned switching means and adapted to control said volume control unit to reduce the volume level of the central station receiver when the central station transmitter is so connected.

e. l'n a communication system having a central station and one or more subscribers stations, a plurality of phonograph reproducer mechanisms, a receiver and a telephone transmitter located at said central station, a speaker and a transmitter located at each of said subscribers stations, a two-wire metallic circuit connecting the speaker at each subscribers station to a corresponding phonograph mechanism, electrical connections asociated with each of said two-wire circuits and forming therewith a plurality of corresponding grounded half-phantom circuits each connected to the corresponding subscriberstransmitter, keying means adapted selectively to connect the central station receiver to any one of said half-phantom circuits and to condition a connection for the central station transmitter to the corresponding two-wire circuit, and switching means adapted to complete said last mentioned connection.

5. In a communication system having a central station and one or more subscribers stations, a plurality of phonograph reproducer mechanisms, a receiver and a telephone transmitter located at said central station, a speaker and a transmitter located at each of said subscribers stations, a twor-wire metallic circuit connecting the speaker at each subscribers station to a corresponding phonograph mechanism, electrical connections associated with each of said two-wire circuits and forming therewith a plurality of corresponding grounded half-phantom circuits each connected to the corresponding subscribers transmitter, keying means adapted selectively to connect the central station receiver to any one of said halfphantom circuits and to condition a connection for the central station transmitter to the corresponding two-wire circuit, switching means adapted to complete said last mentioned connection, an amplifier operating the central station receiver, a volume control unit associated therewith, and switching means automatically operated with said rst mentioned switching means and adapted to control said volume control unit to reduce the volume level of the central station receiver when the central station transmitter is so connected.

6. In a communication system having a central station and a subscribers station, a phonograph reproducer mechanism, a coin register device, a signal relay, a signal lamp, a telephone receiver and a telephone transmitter located at said central station, a speaker,'a transmitter and a coin receiving device at said subscribers station, electric circuits between said stations adapted to connect the phonograph reproducer and the central station transmitter to the speaker, to connect the coin receiving switch to the coin register to actuate the latter each time said switch is actuated and to connect the subscribers transmitter to the central station receiver, a normally open switch connected to make and break the last mentioned connection, an electric circuit for said signal relay controlled by operation of said coin register and actuating said relay, a hold-in circuit i'or said relay adapted to retain the same in actuated condition thereafter, a circuit for said signal lamp controlled by said relay to actuate said lamp when said relay is actuated, and a normally closed switch in said hold-in circuit automatically operable with said normally open switch to release said relay and extinguish said lamp when said normally open switch is closed.

7. In a communication system having a phonograph mechanism at a. central station, and a speaker at a subscribers station electrically connected to and operated by said phonograph mechanism, the combination of a transmitter at said subscribers station, a receiver at said centrai station, electric connections between said transmitter and' receiver including a normally open switch for making and breaking said connections, a coin operated switch at said subscrtbers station. a signal lamp at said central station, a normally closed switch automatically operated with said normally open switch, and electrical means for actuating said lamp including a stick relay operated by actuation of said coin switch and released by opening of said normally closed switch.

LA MAR E. HAYSLE'IT. FRANCIS M. SCHMIDT.

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