Summary
'Magic Eye' tuning indicators were used to assist accurate tuning of radios. They were driven by the AVC voltage which goes more negative with increasing signal strength. This example has dual sensitivity. The EM4 had dual sensitivity with one pattern closing at -5 volts and the other at -16 volts; this made it useful over a wide range of signal strengths. 6.3 volt indirectly heated cathode at 200 ma. anode 250 volts.
Physical Description
Tubular glass bulb has been almost completely removed revealing the valve's internal structure. Part of the glass is separate from the object. Base with 8 side contacts (P base). Mounted on display block.
More Information
-
Collection Names
-
Collecting Areas
-
Acquisition Information
Donation from J. C. Liddy, 27 Apr 1951
-
Manufacturer
-
Inscriptions
Separated piece of bulb: PHILIPS/Miniwatt/EM4/C91 Display block: Description and name of donor. Some of the information on the display block is incorrect: The heater current is actually 0.2 A.
-
Brand Names
-
Classification
-
Category
-
Discipline
-
Type of item
-
Overall Dimensions
70 mm (Length), 26 mm (Outside Diameter)
Not including display block
-
References
Philips Technical Library vol. 2. page 144.
-
Keywords