Made from dark brown
Bakelite.
The volume can be adjusted in 5 steps with the ribbed
knob.The
Philips Radio logo and the text "Ned.O.a 57409" are
printed on the front and back of the plug.
This patent number is
from 1931, it was extended in 1934 and it expired in
1954. The inventor was Willem Six.The official
name of the patent was: "Device in particular for the
control of loudness in low-frequency distribution
systems".
Deze pagina is voor het laeatst bijgewerkt op
zondag 24 november 2019
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