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1947-48 Theatre Catalog, 6th Edition, Page 363 (349)

1947-48 Theatre Catalog, 6th Edition
1947-48 Theatre Catalog
1947-48 Theatre Catalog, 6th Edition, Page 363
Page 363

1947-48 Theatre Catalog, 6th Edition, Page 363

Wireless System for Theatre Hearing Aids

A Portable Instrument Receives HBroadcast"

From Audio-Frequency Induction Transmitter

A principle used by the British Armed Forces during the war for communications around bridegheads has been turned to the peacetime assignment of enabling deafened theatre patrons to hear the sounds of moving pictures from any seat in a theatre. The first American post-war installation of this type of hearing aid was made in the Miami Theatre, Miami, under the supervision of Charles S. Lehman.

The equipment%alled the Telesonic system-has as its biggest advantage the fact that it requires no direct connection between the sound of the picture and the receiver which the hard-of-hearing patron uses. Thus, it is possible for the patron to sit anywhere in the theatre he wishes. The older type of hearing aid requires that hard-of-hearing patrons sit in specific seats which had direct wire connections with the sound system.

Secret of the new system is the creation of a magnetic field, circulated by a loop of wire which runs throughout the theatre. The receivereabout the size of a cigar box, with attached earphoneepicks up the circulated waves by induction and transforms them into sound, amplified to suit the listeners needs.

The system is the invention of Joseph Poliakoff and Oswald Barber Sneath, of London, and, through D. Young and Company, chartered patent agents, registered in Great Britain. On August 12, 1941, through representation by the office of Norris and Bateman, patent attorneys, United States patent No. 2,252,621 was issued.

In the absence of a more elaborate technical presentation and a detailed description of installation, use, and maintenance of what the patentees call a thethod of and Apparatus for the Transmission of Speech and Other Sounds," the patent, the claims excepted, is here printed for the record.


The invention relates to a method of transmitting speech and other sounds, including recorded speech and sounds, within a limited space such as the auditorium of a cinema or theatre, or a sports arena; and to transmitting apparatus and receiving apparatus for carrying the method into practice. The invention is particularly intended for assisting people who are deaf or hard of hearing to receive speech and other sounds through headphones or bone conductors by the aid of a portable apparatus. It has thus the adVantage over systems of deaf aid commonly installed in cinemas and theatres, that the deaf person can hear with a small portable instrument or receiving apparatus from any seat or can move about and does not have to plug it into one of a number of fixed points.


According to this invention, the transmission takes place by audio-frequency induction between a conductor carrying an undulatory current and a pick-up coil energizing a portable receiver. The transmitting apparatus comprises a power amplifier such as is commonly used for public address and allied purposes, the output of which is delivered to a single length or network of conductors deposed about the hall or auditorium. The limited space within which the transmitted signals can be efiiciently received lies within and around the coil formed by the transmitting conductor or it may be restricted to a region adjacent to the said conductor when the size of the coil or loop is very large. The receiving apparatus comprises a thermionic amplifier having combined therewith a pick-up or receiving coil which may be connected by suitable flexible leads to the apparatus, and in the case where the amplifier is a deaf aid appliance having a microphone, may be arranged so that it can be switched in to replace the microphone or it can be effective simultaneously with the microphone.

The invention is illustrated by way of example in the accompanying drawings in which:

Figure 1 shows diagrammatically one form of transmitting apparatus according to this invention.

Figures 2 to 5 show modified arrangements of the transmitting conductor.

Figure 6 shows diagrammatically one form of the receiving apparatus, and

Figures 7 to 9 show modifications of the receiving apparatus.

Figure One

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The output from a thermionic amplifier 1 is connected to a transmitting conductor 4 that forms loops 5 and 6 which enclose areas that are approximately equal although not necessarily similar shape. Such loops may, for example, be arranged in the balcony of the cinema and have the current fiowing therein in opposite directions. Thus the direction of the flow of current in the loop 5 is clockwise whilst in the loop 6 it. is counterclockwise, whereby a substantial neutralization of the fields of the two loops beyond a desired distance, that is outside the cinema, is obtained.

Loops 7, 8, 9, and 10 in series with the loops 5 and 6, are arranged in another part of the cinema, for example the ground fioor. The transmitting conductor is preferable earthed as shown at 11 to prevent the said conductor from having a potential to earth other than that due to the small a.c. potential across the output terminals of the amplifier. Moreover, the parts of the transmitting conductor that form leads between the amplifier and the loops and between the several groups of loops, should be kept parallel to one another and close together so as not to produce a substantial field in themselves, such leads being, if desired, arranged in conduits in such a manner similar to mains wiring. The amount of power necessary for the satisfactory working will, where there is no outside electrical interference, be determined by the am 'plification of the receiving apparatus,

but it will in practice frequently depend upon the power needed to mask interference by other electrical apparatus.

Figures Two and Three

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Figure 2 shows a modified arrangement of the loops of a transmitting conductor in which loops 12 to 19 are in series. The loops 12, 14, 16, and 18 have the current fiowing therein in a clockwise direction, whilst in the loops 13, 15, 17, and 19 the current fiows counterclockwise. The area enclosed by the loops 12, 14, 16, and 18 is made substantially equal to the area enclosed by the loops 13, 15, 17, and 19, for the reason set forth above. In some cases however, the loops, or series of loops forming the transmitting conductor, are arranged in parallel. In this case, to obtain neutralization at a distance, the aggregate of the products of the currents flowing clockwise by the areas enclosed by the loops conducting such currents, must equal the aggregate of the product of the currents fiowing counterclockwise by the areas of the loops conducting such currents.

Figure 3 shows an arrangement of transmitting conductor in which the areas enclosed by loops which are in series and in which the current fiows respectively clockwise and counterclockwise directions are substantially equal. In this case the transmitting conductor is formed into a large loop 20, in which the direction of flow is clockwise, and loops 21, 22, 23, and 25 in which the direction of flow is counterclockwise, all of the said loops 20 to 24 being in series.
1947-48 Theatre Catalog, 6th Edition, Page 363