US1676668A - Telephone transmitter - Google Patents

Description

TELEPHONE TmmswilTTERA Filed March 5, 1925 Side af INVENTO'R H. J. RQUND JUNITED STAT-Es n EN FICE.

'HENRY`JOSIPH\RUND, 0F LONDON, ENGLAND, A SSIGNOR TO RADIO CORPORATIGN OF AMERICA, A CORDORATION OF DELAW'AREI.l v

TELEPHONE TRANSMITTER.

Application 1aed March 3, 1925, serial No'.

I 'I his invention relates to. telephone transmitters of the magneto-phone type'ln Which the movements of a coil suspended 1n a mag- Anetic ield and moved by the incidence of sound Waves up`on it produce differences of potential' which are stepped up by ta trans'- formerand applied tothe grid of a thermionic valve by which they are ampliied.

According to this invention the coily is constructed in the form of a spiral and is mounted upon an annular support formed ofl thin paper or other suitable material, the

' Weight of' the wire being equal -or substany impaired unless the paper b e heavier andA tially equal to the Weightof the support and of the adhesive by which Ithe Wire is secured to the support. f l

The resistance 'f thecoil is chosen so that the damping resistance usually inserted in shunt across the secondary of the transformer may be omitted. e

Preferably NI employ tissue 4paper and aluminium Wire. With this paper the spacf ing of the Wire, which4 is about No. 40,

S. W. G., should not exceed 2 mm.; other stiffer. Such an arrangement Will not'be so sensitive.

It 1s usual to glve to speech transformer a natural resonance of about 1000 cyclesper second and by shunting the secondary with a resistance of about 250,000 ohmsfairly uniform, response lfor.

the range from 100 to 5 000 cycles can beobtained. But With any particular-transformer the exact value ofthe shunt resistance to obtain the required response curve may be determined experimentally.

-the Secondary of 'a' 12,912, and in Great isritain Maren 3, 1924..

coil connected to the primary coil equivalent al resistance in shuntto the secondary will be required so that the maximum voltage may be obtained Whilst the resonance curve remains Hat.

The invention is illustrated in the accompanyino drawing, of which Figure lis adiagram .showing the coil l of the telephone connected tothe primary "2 of a step-up transformer Whose secondary 3 is connected` to the grid of a thermionic valve 4. y

Figures 2 -and 3 are respectively ia section and afront elevation of the telephone.-

Refe'rringto Figures 2 and 3, 1 is the telephone coil, 5 an'aznular paper support, and 6 and 7'are. the poles of a magneto-phone magnet or electromagnet. Having-described my invention What I v1. In a telephone apparatus of the magneto-phone type, an electromagnet having an annular air gap, a fiat aperiodic annular diaphragm supported therein, and a flat spiral coil secured tosaid diaphragm.

I 2. Ina telephone apparatus of the magneto-phone type, an electromagnet having a magnetic field, anf annular diaphragm suspended within the magnetic field;- ofsaid electromagnetya flat spiralA coil and .means for securing said coil to said diaphragm so that the Weight of said Vdiaphragr'ri and said se'-l curing means is approximately equal to lthe Weight ofsaid coil. "i I l [3.' Ina telephonel apparatus of the magneto-phone vtype,l an electromagnet having a'magn'etic field, a flat annular paper iia phragm suspended Within the magnetic field 'of said electromagnet, a flatspiral aluminum Wire coil the spacing ofsaid Wiremot exceeding 2 mm; and means for` securing said coil to saddiaphragm. By making the resistance of thel telephone HENRY JOSEPH ROUND.

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