English: French 4 valve regenerative radio receiver from 1919. Invented in 1913 by Edwin Armstrong, the regenerative receiver was widely used until it was superseded in the 1930s by the superheterodyne receiver. This one uses 4 valves; a regenerative detector, followed by 3 audio amplifiers to provide enough power to drive the horn loudspeaker. It uses the Armstrong or "tickler" circuit, in which the signal from the plate circuit of the detector tube is fed back into the grid circuit by magnetically coupled coils, to increase the gain and selectivity. This is accomplished by the dual "honeycomb coil" vario-coupler (left). One coil is the tuned circuit of the receiver, connected to the grid. The other is the "tickler" coil in the plate circuit. The coils are hinged so they can be moved together or apart to change the coupling, which controls the amount of feedback.
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{{Information |Description=*{{it|ricevitore a plato a quattro valvole}} *''year'': 1919 *''note'': made in France |Source=Own work |Date=''see exif'' |Author=User:Iron Bishop |Permission=Own work, copyleft: Multi-license with GFDL and Creative Common