|
US1952809A
|
|
Sound reproducing apparatus
|
|
US1852419A
|
|
Film advancing appliance
|
|
US1808046A
|
|
Film of magnetizable material for episcopic projection
|
|
US1765923A
|
|
Apparatus for making sound records
|
|
US1877731A
|
|
Sound reproducing appliance having alpha film record
|
|
US1742085A
|
|
Talking machine
|
|
US1816782A
|
|
Sound reproducing device
|
|
US1747778A
|
|
Head telephone
|
|
GB261369A
|
|
Improvements in and relating to films
|
|
US1835164A
|
|
Process for recording sound for talking machines
|
|
US1789104A
|
|
Transmitter for telephony
|
|
US1752185A
|
|
Acoustic apparatus, particularly signaling apparatus
|
|
US1799378A
|
|
Method of and system for reproducing sounds
|
|
GB246124A
|
|
Improvements in gramophones
|
|
GB246376A
|
|
Improvements in gramophones
|
|
US1775248A
|
|
Method of and apparatus for increasing the volume of mechanicallyreproduced sounds
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