US1412539A - Telephone - Google Patents

Description

R. L. MURRAY.

TELEPHONE.

APPLICATION FILED SEPT. 16, I920.

1,412,539. Patented Apr. 11, 1922.

UNITED STATES PATENT OFFICE.

ROBERT LAMBERT MURRAY, 01 BUSHEY HEATH, ENGLAND, ASSIGNOB TO THE TELE- PHONE MANUFACTURING COMPANY, (1920) LIMITED, OF LONDON, ENGLAND, A BRITISH LIMITED LIABILITY COMPANY;

TELEPHONE.

Specification of Letters Patent.

Patented .Apr. 11, 1922.

To all whom it may concern:

Be it known that I, ROBERT LAMBERT MURRAY, a subject of the KinIgI of England, residing in Bushey Heath, ertfordshire, England, have invented certain new and useful Improvements in Telephones, of which the following is a specification;

This invention relates to telephones-and in particular to a receiver and transmitter secured together as an unitary device somewhat after the manner of what are known as hand-combinations.

The term hand-combination is hereinafter employed to denote any construction in which a users transmitter and receiver are secured together as an unitary structure, whether or no it is to. be held in the users hand.

One object, and-the principal object, of this invention, is to reduce the loudness of what are known as sidetones, and particularly in hand-combinations whereof the transmitter is to be held against the users throat.

In back-to-back hand-combinations known heretofore it has been considered necessary to employ between the transmitter, and re ceiver a filling material to act as a damper to prevent the phenomenon known as howling. We have found that such damper can be dispensed with when the microphone and receiver, whereof the resistances are in a pre-determined ratio one to the other, are

directly connected in parallel with one another, and the microphone and receiver can therefore be both directly secured, with obvious advantages, on a rigid metallic mounting extending between the same. It has heretofore been known to connect a transmitter and receiver at a station in parallel with one another for use with a common battery; in one such known arrangement an induction coil had its primary winding connected in series with the microphone and its secondary winding in series wit the receiver. By dispensing with the use 'of an induction coil the construction is still further simplified and the cost of manufacture reduced.

According to the present invention, therefore, a telephone hand-combination has its microphone and-receiver connected directly in parallel with one another, and the points of electrical junction of the said two parts are connected directly to the transmission lines, for the purpose of reducing side-tones.

Preferably, the at-rest resistance of the microphone and that of the receiver at a station are approximately in the ratio of 2 :1.

According to another feature of the invention, a telephone hand-combination wherein the microphone and receiver are mounted back-to-back on a support common to them both and are connected electrically in parallel with one another when operated, is characterized by the support being in the form of a rigid metallic mounting extending between and directly secured to the microphone and receiver.

Conveniently, a telephone hand-combination having its microphone and receiver connected as described above is arranged for common battery operation and in such a manner that the said battery always tends to strengthen the permanent magnetism of the receivers.

The accompanying drawings illustrate a construction of divers telephone embodying this invention,

Figure 1- being a perspective view of a transmitter and receiver arranged as a handcombination Figure 2 being a central vertical section through the instrument on the line 22 of Figure 3;

Figure 3a front elevation with the receiver.

diaphragm and itsjcap removed, and

Figure 4 a diagram of the circuits.

Dealing first with the arrangement of the circuits, they are so arranged that the receiver R and transmitter T are at one station connected in parallel with one another and through the lines L-L to the transmitter T and receiver R at the other station which transmitter, and receiver are again in parallel with one another.

Dealing with the actual construction shown in Figures 1-3, a cup-shaped foundation A is provided, screw-threaded externally at A to engage the receiver-cap B and at A to enga e the transmitter-cap. C. The receiver diap 'ragm is indicated at B and the transmitter diaphragm at C, each being clamped in position by its res ctive cap, the diaphragm B. directly to t e upstanding wall A of the foundation and the diaphragm C by means of a loose mg C interposed between the cap C and the bottom of the foundation A.

On the right-hand-side of,the bottom of the foundation, as viewed in Figure 2, is mounted the microphone D, and on the lefthand side the ieceiver magnets seen at E. These magnets are each in the form of a semi-circle and are held in position with their similar poles opposing one another and in very close proximity to one another, each pole being provided with a slight semi-circular groove to accommodate the stem of a fixing screw E One of these fixing screws further serves, by means of a lug F to hold the outer pole-piece in the form of a ring F in position, while the other holds a core, concentric with the ring F, in position, by means of a lug G. The core is not seen in the drawing bein surrounded by the usual operating coil i A'curved plate spring H isprovided on the inner face of the wall A so as to constitute a spring key for which a chin-push H is provided. One end of the spring is secured by screws to the wall'A and the other end is free to be operated by the push H and make contact atH with a contact plate held between blocks H of insulating material against the wall A The usual three flexible leads J, J, J? are brought in through the wall A at a point opposite the push H and are connected in any convenient manner to their appropriate parts of the" device so as to constitute a ringing and speaking circuit in the usual well-known manner. As shown in Figure 4 a one-way ringing circuit comprising a bell X is provided.

On the outside of the cap B of the receiver, which cap serves totally to enclose the diaphragm B, there is mounted a connector K communicating by a central perforation K with the space between the inside of the cap and the diaphragm B, and by means of lateral perforated branches K with flexible tubes, not shown in the drawing, serving to conduct the sound to the users ears.

A strap M is provided to enable the device to be secured to the users neck so as to present the cap C to the throat in the neighbourhood of the larynx and so that the user can readily depress the push H with his chain.-

In connecting the apparatus up care is to be taken that the battery Z and the coils G are so interconnected that the effect of the battery is always to tend to strengthen the permanent magnets of the receivers.

Contrary to what might be expected, it is found with the apparatus constructed and connected in the manner just above described, the nser is not troubled with what are ordinarily known as side-tones, in spite of the fact that the transmitter is mounted directly upon the receiver. The coil G and the microphone Dare constructed to have resistance values such as are ordinarily employed for telephonic communication over reasonable distances for diving operations and the like, and by means of ordinary line wires 01' cables. For example, the receiver coil may have a valueof- 15 ohms and the transmitter an at-iest resistance of 25 ohms. The instrument as thus constructed does not howl and it is believed that contributary causes to this satisfactory result are to be found in the existence of the solid bottom A of the foundation between the receiver and transmitter, and, in an even more important degree, to the'arrangement indicated in Figure 4. It will readily be-u'nderstpod that variations inthe transmitter resistance will not, when the parts are arranged in par allel as shown, act so directly-upon the receiver as when they are connected in series in the usual manner. It is well-known with the receiver and transmitter in series with one another as is usual, a telephone may be made to howl, as it is called, by holding the receiver opposite to the transmitter and the tendency to do this has heretofore militated against success of instruments in which the receiver and transmitter were mounted in very close proximity to one another and each'mechanically supporting the other.

What I claim as my invention and desire to secure by Letters Patent is '1. In a telephone system between two sta-r tions the combination of a transmitter and a receiver at one station mounted back to back upon a support common to them both, connections connecting the receiver and transmitter directly in parallel with one another, a'receiver and transmitter at the other station mounted and connected in relation to one another as are those at the first said station, a speech-transmitting conductor connected at one end directly to one point of electrical junction between receiver and transmitter at one station and at the other end directly to the point of junction between transmitter and receiver at the other station, a battery and a second speech-transmitting conductor connected at one end directly to the second point of junction between transmitter and receiver at one station and through sald battery to the second point of junction between transmitter and receiver at the other station, substantially as set forth.

. 2. In a telephone system between two stations the combination of a transmitter and a receiver at one station mounted back to back upon a support common to them both,

the receiver, a receiver and transmitter at the other station mounted and connected in relation to one another as are those at the first said station, and whereof the at-rest.

resistance of the microphone is approximately double that of the receiver, a transmitting conductor connected at one end directly to one point of electrical junction between receiver and transmitter at one station and atthe other end directly to the point of junction between transmitter and receiver at the other station, a battery and a second transmitting conductor connected at one end directly to the second point of junction between transmitter and receiver at one station and through said battery to the second point of junction between transmittel' and receiver at the other station, substantially as set forth.

- 3. In a telephone system between two sta' tions the combination ofa transmitter and a receiver at one station mounted back to back upon a support common to them both, connections connecting the receiver and transmitter directly in parallel with one another, a receiver and transmitter. at the other station mounted -and connected in relation to one another as are those at the first said station, a transmitting conductor connected at. one end directly to one point of electrical junction between receiver and transmitter at one station and at the other end directly to the point of junction between transmitter and receiver at the other station, a battery and a second transmitting conductor connected at one end directly to the second point of junction between transmitter and receiver at one station and through said battery to the second point of junction between transmitter and receiver at the other station in such a manner that the said battery tends always to strengthen the permanent magnetism of the said two receivers, substantially as set forth.

4;. In a telephone system between two stations the combination of 'a transmitter and a receiver at one station mounted back-toback on a support common to them both and connected directly in parallel with one another, a flexible tie extending between two points of attachment therefor to the said support for the purpose described, a bellpush projectin radially outwards from the said support For the purpose described, a receiver and transmitter at the other station connected directly in parallel with one another, a transmitting conductor connected at one end directly to one point of electrical junction between receiver and transmitter at one station and at the other end directly to the point of junction between transmitter and receiver at the other station, a battery 'and a second transmitting conductor connected at one end directly to the second point of junction between transmitter and receiver atone station and through said battery to the second point of junction between transmitter and receiver at the other station, a calling circuit comprising a line wire and a calling device in series with one another whereof one end is connec'ted to the aforesaid bell-push and the other end is connected to the point of junction between the transmitter and receiver at the said second station, substantiall as set forth.

In testimony whereofi aflix m si nature.

ROBERT LAMBERT M R AY.

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