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 a carbon microphone, battery supply, 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.
Engineering record
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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