Equipment photographs · 1
1 / 1 · US patent 1,448,279 (1923): electrodynamic receiver, the Magnavox moving-coil driver
US patent 1,448,279 (1923): electrodynamic receiver, the Magnavox moving-coil driver·Edwin S. Pridham & Peter L. Jensen·Public domain (US patent)
A period Magnavox public-address deployment; the image documents the system in political speech use.
Amplified campaign address, Magnavox equipment, 1920·Anonymous·Public domainWhy it mattered
- 01
Combined microphone, vacuum-tube amplification, moving-coil driver, and a large horn into a recognizable PA system.
- 02
Demonstrated that one speaker could address an outdoor crowd electrically rather than through acoustic megaphones alone.
Original pricing
No reliable period list price located
2026 equivalent
Not calculated without a reliable original price.
Installations were configured as systems; published accounts emphasize demonstrations and commissions rather than a standard package price.
Use in the field
Professional reactions
Later recollection · 1975 (written c. 1942-44)
Jensen recalled that he and Pridham were enthusiastic enough about their new telephone mechanism to give it a name: the Electro-Dynamic Principle. Their account conveys the excitement behind the moving-coil technology that became the Magnavox horn system.
Manuals & original documents
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