Loose coupler
In mahogany housing with ebonite front and knobs nickeled brass contacts.
 Advertisement for a tuning capacitor by the company in Popular Electricity from June 1913
The original price was about $21.
Loose couplers were used in the '10s of the twentieth century. The device consists of two coils, a primary and a secondary.
The primary coil is stationary and is equipped with a compound switch with 34 (16 + 18) contacts so that the inductance of the coil can be adjusted.
The secondary coil can be slid in and out of the primary coil to vary the degree of coupling and is also equipped with a slider and 12 contacts so that the inductance can be changed there too. This model is also called "Navy type transformer".
By means of a "dead end switch", mouted on the panel, the major part of the primary winding may be entirely disconnected from the circuit when receiving on low wave lengths.
A loose coupler was the first tuning tool in an early receiver. The first coil was connected to an antenna and a ground; the second coil was connected to a detector, in most cases a crystal. Wave lengths of 200-4000 meters may be tuned to.
John Y. Parke & Co. made all kinds of technical articles as early as the 19th century. The company was located in Philadelphia, 127 North 7th Street.
Data
Serial number: none

Dimenstions (h x w x d): 16.5 x 47 x 16.5 cm
Made in: 1919
Purchased in: 2021

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