US2094681A

US2094681A - Group audiphone system

Info

Publication number: US2094681A
Application number: US44515A
Authority: US
Inventors: Sterling G Sears
Original assignee: DICTOGRAPH PRODUCTS CO Inc
Current assignee: DICTOGRAPH PRODUCTS CO Inc; DICTOGRAPH PRODUCTS COMPANY Inc
Priority date: 1935-10-11
Filing date: 1935-10-11
Publication date: 1937-10-05
Anticipated expiration: 1954-10-05

Description

Oct. 5, 1937.. s. G. sEARs GROUP AUDIPHONE SYSTEM FiledDc-t. 11, 1955 2 Sheets- Sheet 1 lNvsN-ro 1 AT NEY Oct. 5, 1937. s. e. SEARS 2,094,681v

GROUP AUDIPHONE SYSTEM v Filed Oct. 11, 1935 2 Sheets-Sheet 2 IINVENTOR W RN J CZ Patented Oct. 5, 1937.

UNITED STATES PATENT OFFICE GROUP AUDIPHONE SYSTEM Application October 11, 1935, Serial No. 44,515

6 Claims.

This invention relates to a group audiphone system and has particular reference to a plurality of individual hearing aid devices responsive to a common remote sound transmitting source and especially adapted for aiding the hard-ofhearing among the audience of a theater, the congregation of a church, the assembly of a convention, or any other gathering or groups of persons to clearly hear the entertainment, services, or

0 proceedings, with comfort and convenience.

Inasmuch as it is obviously impracticable to provide a hearing aid device for each seat in a theater, church, or the like, and is impossible to properly distribute a number of such devices to the relatively few deaf persons for actuation from a commonsource of sound; such as the speaker's or actors microphone, the sound reproducing apparatus of a talking picture machine, or the like, the arrangement heretofore has been to provide each seat with a connection box with which a portable hearing aid receiver may be connected by the individual user, the connection boxes being connected in series or parallel with the transmitting microphone and amplifier, talking picture machine, or other source of sound in which the bearer is interested. jHowever', because these individual receivers are usually not connected in the transmission circuit at the same time, the intermittent connection and disconnection of the several receivers by the users creates an almost continually varying load on' the system during certain periods, with the result that the reception of the sound by the several users varies, causing frequent adjustment of their individual volumecontrol rheostats with consequent diversion of attention, nuisance and discomfort.

In accordance with the present invention, a group audiphone system is provided, which may be either temporarily or permanently installed in a theater, church or other auditorium or gathering place with ease and rapidity, which is so arranged that the distribution of the individual receivers may be varied at will according to the number and location of the persons requiring them, which is adjustable in accordance with the distance of the source of sound from the microphone and requires no further adjustment, and with which the transmission of the sound remains uniform, clear and undisturbed, no matter how connected into or out of the circuit during the period of transmission of the sounds.

More particularly, the invention comprises an amplifier provided with a volume control variably calibrated to the distanceof the source of sound many of the individual or groups of receivers are from the microphone and having a resistance or impedance connected across its output terminals, which is substantially equal to the resistance or impedance of the maximum number of individual receivers, and which is disconnected when the 5 load, which is substantially equal to the maximum number of individual receivers, is connected thereto.

This substitute load is represented by complementary resistances or impedances preferably connected in series and located in junction or jack boxes connected by a main cable for distribution at properly located central points throughout the auditorium, the number of such resistances or impedances equalling the number of sub-distributing connections required, .and aggregating a resistance or impedance substantially equal to the substitute load resistance or impedance in the amplifier and consequently substantially equal to the load of the maximum number of individual receivers.

Each of these sub-distributing connection box resistances or impedances is substantially equal to the total resistance or impedance of the corresponding bank of individual receivers allotted to that junction box and is disconnected when this bank is connected to the box. There arecorresponding jack boxes for receivers, and each of them is provided with a resistance or impedance substantially equal to the resistance of the corresponding receiver and disconnected when that receiver is plugged in.

These substitute resistances or impedances for the receivers are preferably connected in parallel, so that the entire distribution system is connected in series-parallel, and the several substitute loads for the indlvidual'receivers, each group or bank of receivers and of the entire distribution system are complementary and correlated in such a way that the amplifier is serving a full load at all times, regardless of the number of receivers in service at any one time and the volume and quality of the sound are unaffected and the reception is undisturbed by clicks or contact noises due to connection or disconnection of one or more receivers in the system during the period of the sound transmission. This series-parallel arrangement also protects the system and apparatus against injury as the result of short-circuiting of a jack, for example by an extraneous conductor inserted therein, a short-circuited receiver cord, or sub-distribution cable, or the like. Also, broken or otherwise open receiver cords or the like, are prevented from afiecting the system in a detrimental way. 55

The receiver jack boxes for temporary or portable installations comprise housings provided with a clamp or hook whereby they may be supported on or by the rear of the chair or seat in front of the user and are connected to the redistributing cable. Each of these portable jack boxes contains the substitute load resistance for the corresponding individual receiver, and is fitted with a jack for receiving the plug of the receiver, which is suspended from a hook on the jack box when not in use. A.flat plug having little lateral projection is provided and the cord connecting the receiver thereto is preferably fitted with a volume control rheostat. For permanent installations such as for theaters, in which the amplifier is connected directly to the sound-reproducing apparatus of the talking picture machine, the receiver jack boxes are preferably secured to the underside of every other arm and are provided with double jacks, one for each adjoining seat.

It will be seen that with the group audiphone arrangement of this invention, a very simple, fool-proof and efiective system of sound distribution for the hard-of-hearing is provided, which may be readily installed and operated with a minimum of labor and with a maximum of effectiveness and satisfaction to the users. Further advantages of the-invention will become ap-. parent upon examination of the accompanying drawings, in which:

Figure 1 illustrates the manner in which the group audiphone system of this invention may be installed; 7

Fig. 2 is a distribution wiring diagram of the same;

Fig. 3 is an enlarged perspective view of one o the portable jack boxes;

Fig. 4 is a distribution wiring diagram for a theater; and

Fig. 5 is an enlarged view of the amplifier range adjustment dial.

Referring to Fig. l of these drawings, numeral Ill designates a microphone located on a stage or rostrum I l or the like and connected by a cable I l to an amplifier l2, which is energized from a suitable source of power connected thereto by cable 13 and which is provided with a jack adapted to receive the plug N connected to the main distribution cable l5. In a temporary. installation this distribution cable is laid along the floor, such as along the aisle of the theater or the like, and is provided at spaced intervalswith jack boxes IS, the number of which depends upon requirements, such as the number of tiers-of seats or chairs to be served.

Jack boxes l6 preferably have two jacks to p which are connectible by suitable plugs I! the subdistribution cables l8 leading-to a plurality of individual jackboxes l9 preferably supported on the seats or chairs immediately in front of the position where the hea ers sit, as is indicated in Fig. 3. These individual jack boxes H) are each provided with a spring hook or clamp 20' adapted to support the box on the back of the chair, and a hook 2! or the like on its underside upon which the headband 22 of the audiphone receiver 23- may be conveniently suspended when the re-" ceiver is not in use.

The audiphone receiver 23 may be of the conventional air conduction type or may be of the bone conduction type, as is illustrated, and adapted to be held against the bone structure of the user, such as on the mastoid eminence behind the ear, by means of the headband 22, The electric cord 24 leading from the receiver 23 is fitted with a volume control rheostat 25 and with a fiat plug 26,adapted to be inserted in the jack box l9. The head of the plug 26 is made fiat, as

The arrangement illustrated is convenient and satisfactory for a temporary installation but if a permanent installation is required the cables I5 and I8 may be laid in conduits in thefloor or the like, the amplifier l3 concealed and the microphone l located at suitable points, such as at Hi. 1

As is illustrated in the wiring diagram of Fig. 2, the output terminals 21 of the amplifier l3 are bridged by a resistance 28, which is substantially equal to the predetermined full load of the group audiphone system, so that, whether or not the plug I l of the main distribution cable I is plugged into the jack 29, the load on the amplifier I2 is constant. The contact spring 30 of the jack 29 when engaged by'the tip 3| of the plug I4 is moved out of engagement with the contact 32, to which one end of the resistance 28 is connected, so that the latter is disconnected from the output circuit of the amplifier l2. Simultaneously, the engagement of the tip and sleeve of the plug with the contact spring and sleeve of jack 29 connects the main distribution cable I 5 into the amplifier output circuit. Withdrawal of the plug I6 releases contact spring 30 so that it reengages contact 32 and reconnects resistance 28 across the output terminals 21 of the amplifier i2.

By way of illustration, if the plan of the auditorium requires as many as ten subdistribution cables I8 in order to secure proper distribution of the individual audiphone receivers 23, ten resistances 32 are preferably connected in series in the main distribution cable l5, each of these resistances being substantially equal to the full load of the corresponding subdistribution cable I 8 and all of them aggregating a total resistance which is substantially equal to the resistance of resistance 28 in the amplifier. For example, if the total predetermined load on the amplifier is 100 ohms the resistance of each individual resistance 32 is ten ohms.

In the arrangement illustrated in Figs. 1 and 2, two of such resistances are placed in each subcontacts 35, disconnecting the resistance 32.

Contact spring 34 is connected to the correspond- -ing wire of main distribution cable I 5 on one side of resistance 32 and the sleeve of the jack 33 is connected to the opposite side of the resistance 32, so that the insertion of plug I'I efiects connection of the subdistribution cable I 8- to the main distribution cable l5.

The plurality of individual jack boxes I 9 of subdistribution cable I8" each contain the jack 31 and a resistance 38, which is substantially equal to the resistance of the audiphone receiver 23. The resistances 38 are connected in parallel in subdi'stribution cable l8 and are so arranged that their net resistance is substantially equal to the resistance of resistance 32; For example, if the resistance of audiphone receiver 23 is 50 ohms and there are five individual jack boxes I!) for each subdistribution cable l8, the resistance 38 in each of them is substantially equal to 50 ohms, and since there are five individual jack boxes IS, the net resistance of the five resistances 38 is 10 ohms, according to the reciprocal rule regarding parallel resistances.

Each individual resistance 38 is preferably connected at one end to one of the wires of the subdistribution cable I 8 and at the other end to contacts 39 normally closed by contact spring 48 of the jack 31, which is connected to the other wire of the subdistribution cable l8. When the plug 28 of the audiphone receiver 23 is plugged into jack 3! the tip of the plug causes contact spring 48 to disengage contact 33, thereby disconnecting resistance 38.

In operation, each of the elements of the group audiphone system of this invention is represented by a substitute load, so that the system is under full load at all times, no matter how few or how many of the individual audiphone receivers 23 are in use and no matter how few or how many of the subdistribution cables 18 are in use. Thus, the main distribution cable i may be laid and, as each of the subdistribution cables is connected by its plug I! to the corre-' sponding 'jack box ill, the resistance 32 corresponding to thesubdistribution cable, is disconnected and substituted by the net resistance of the individual. -r esistances 38, which is substantially equal to resistance 32. Similarly, as each of the individual audiphone receivers 23 is plugged into a jack box IS; the resistance thereof is substituted for the resistance 38, which is disconnected but which is reconnected and becomes a substitute load for the audiphone receiver 23 when the latter is disconnected.

With this arrangement, there is no fluctuation in the load on the amplifier of the group audiphone system and none of the individual users is disturbed by clicks or a change in reception by the connection and disconnection of individual audiphones during the period of the sound transmission, so that transmission remains clear and uniform under all operating conditions Also the present arrangement provides a very flexible and simple system which may be installed in many different ways to suit circumstances and requirements.

For permanent installations, and especially those in theaters or the like, where the amplifier I2 is directly connected to the sound reproducing apparatus of talking picture machine, or the like, the individual jack box installations may be more or less permanent and attached to the under side of every other arm of the seats. To that end the arrangement illustrated in Fig. 4 is utilized in which the jack boxes 39 are suitably secured to the under side of the seat arms and are provided with opposite jacks, one for each adjacent seat. The substitute load resistances 4| for the two corresponding audiphone receivers 23 are connected in series in the series-parallel arrangement of the subdistribution cable i8.

The sleeve of the jack 48 is connected by a wire 42 to one end of the corresponding resistance 4|, and the contact spring 43 of the jack 40' normally closes contacts 44 connected to the other end of the resistance when the plug 26 of the audiphone receiver 23' is inserted in jack 48', its tip causes contact spring 43 to disengage contacts 44, disconnecting resistance M from the circuit. Conversely, when plug 23' is withdrawn, contact 43 is released to close contacts 44 to reintroduce substitute load resistances 4| into the distribution circuit. As shown in Figs. 3 and 4 the audiphone receivers 23 and 23' may be held by headbands 22, or by the handle 45, and a volume control rheostat '25 of the button type may be used or one of the slider type, such as indicated at 46 in Fig. 4, may be used.

The location of the source of sound from the microphone ill or ill normally determines the degree of amplification necessary for the audiphone system. Accordingly, the rheostat'of the amplifier of this invention is calibrated to the distance of the source of soundfrom the micro! phone. For example, if the distance X of the speaker is ten feet from the microphone ill in Fig.= 1, rheostat 41 is adjusted so that its pointer -48 indicates III on the dial 49, which is subdivided into feet of microphone range, as is indicated in Fig. 5. This adjustment remains constant for all transmission purposes and need be varied only when the distance of the source of sound of the microphone l0 varies materially.

While several preferred embodiments of the invention have been illustrated and described herein, it is to be understood that the invention is not limited thereby, but is susceptible of changes in form and detail within its scope. The term resistance as used herein and in the appended claims is regarded for purposes of this application as synonymous with or comprehending an impedance.

I claim:

1. In a group audiphone system, the combination of a source of sound transmission, a main distribution line connected thereto and having a plurality of spaced resistances connected in series and having a total resistance substantially equal to the predetermined full load of the system, a plurality of subdistribution lines adapted to be connected individually across each of, said resistances for disconnecting them, a plurality of spaced resistances connected in parallel in each subdistribution line and having a total resistance substantially equal to the corresponding resistance in the distributing line, and a plurality of audiphones each adapted to be connected across a subdistribution line resistance for disconnecting it and having a resistance substantially equal to said subdistribution line resistance, whereby the load on the source of sound transmission remains constant regardless of the connection and disconnection of the several subdistribution lines and audiphones in the main distribution line.

2. In a group audiphone system, the combination of a source of sound transmission, an amplifier therefor, a resistance across the output terminals of the amplifier and. substantially equal to the predetermined full load of the system, a distribution line ccnnectible across the output terminals of the amplifier for disconnecting the said resistance, a plurality of resistances in said distribution line substantially equal in total resistance to the said predetermined full load of the system,- said resistances being connected in series, a plurality of subdistribution lines adapted to be connected individually across each of said resistances for disconnecting them, a plurality of spaced resistances connected in parallel in each subdistribution line and having a total resistance substantially equal to-the corresponding resistance in the distributing line, and a plurality of audiphones each adapted to be connected across a subdistribution line resistance for disconnecting it and having a resistance substantially equal to said subdistribution line resistance, whereby the load on the source of sound transmission remains constant regardless of the connection and disconnection of the several subdistribution lines and audiphones in the main distribution line.

3. In a group audiphone system, the combination of a source of sound transmission, an amplifier connected thereto, a plurality of spaced jack boxes, a distribution cable connecting said boxes to the amplifier, a plurality of subdistribution cables, a plug for each of said subdistribution cables for connecting the latter to corresponding jack boxes, spaced jack boxes in each subdistribution cable, an amplifier for each subdistribution jack box having a plug for connection with the latter, a resistance in each subdistribution cable jack box substantially equal to the resistance of the corresponding audiphone and adapted to be disconnected by the plug of the latter, a resistance in each distribution cable jack box substantially equal to the total resistance of the subdistribution cable and adapted to be disconnected by the plug of the latter, whereby the load on the system remains constant regardless of the connection and disconnection of the audiphones and subdistribution cables in or out of the system.

4. In a group audiphone system for theaters and the like, the combination of a source of sound, a remote jack box supported on alternate seats of a row, double jacks on the jack box connected in series to the source of sound, a resistance connected across the contacts of each jack, and a normally-closed switch between one side of the resistance and one of the jack contacts adapted to be opened by a plug inserted in the jack.

5. In a groupaudiphone system, the combination of a microphone, an amplifier connected thereto, a rheostat in the amplifier circuit for controlling the output volume thereof, a dial for the rheostat divided in increments of distance of the source of sound from the microphone, and a plurality of audiphones connected to the amplifier.

6. In a sound transmission system, the combination of a transmitter, an electrical sound amplifier connected thereto, a receiver connected to the amplifier, an adjustable volume control for the amplifier, a pointer thereon, and a dial for the pointer divided in increments of distance of the transmitter from the source of the sound to be transmitted.

STERLING G. SEARS.