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| illustration of the valve set used in
the radio receiver model 2515 made in Holladn by Philips.
The arrow shows the rectifying valve model 506 |
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| One of the first radio receivers for
operation in 110-220V, AC, model 2515 made in Holland
by Philips showing (a) its rectifying valve type 506 |
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| Communication receiver model GR-78,
mde in the USA by Heath. The arrows shows in its front
panel the automatic volume control. |
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| Block diagram of the Hi-F audio amplifier
model 80 AZ made in the USA by Fischer. The dotted line
shows the allocation of the negative feedback section
in its circuit. |
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| Radio receiver model 3000-1 made in
the USA by Zenith. The arrow shows in the front panel
its automatic frequency control |
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| close up of the radio receiver model
Royal 3001-1 showing the automatic frequency control |
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| Model 80 AZ Hi-Fi audio amplifier, manufactured
in 1957 by Fischer Company, EUA. |
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