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History of the manufacturer  

Duovac Radio Tube Corp.; Brooklyn, NY

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Name: Duovac Radio Tube Corp.; Brooklyn, NY    (USA)  
Abbreviation: duovac
Products: Tube manufacturer

Duovac Radio Tube Corp.
360 Furman Street, Brooklyn, NY

After the meters and the "Shadowgraph" tuning aids - or the bulbs - the Neon filled tuning indicators came into use - until the magic eyes took over. The neon tuning indicator was introduced by Duovac in a one-shot ad in the July 1931 issue of "Electronics". Duovac stamped the base as "DUOVAC TUNE-A-LITE - PAT. PEND." The bulb is a slender glass tube 3-1/2" in length and 1/2" in diameter with a bayonet base.

Different radio manufacturers introduced this device as "Tonebeam" (Atwater Kent 1932) or "Flash-O-Graph" (Fada). Another neon indicator is the "Tuning Flasher" NE-16 (991) used for Sears 1722 and 1732 sets ca. 1934. In GB (UK) Cossor and MOV (Marconi Osram Valves; GEC) produced it as "Neon Tuning Indicator" 3180 and 3184. A "Tuneon" (as solely power indicator with a three-pin base) was built until at least 1946. "Radio-Technique" 4662 in France (Philips) has a four-pin base.

In the February 1933 issue of "Electronics" a four-electrode version was introduced as resonance indicator. The extra electrode could be used to mute the receiver when tuned between stations (noise -squelch, noise gate, noise suppressor). Fada model RW from ca. 1933 does use it as "Type N-4" - also for interchannel noise suppression. The year before Fada applied the three-wire version in RA and RC models as "Flash-O-Graph". We may have to arrange these indicator types in three separate sections embracing two-, three-, and four-electrode devices separately.


Further details for this manufacturer by the members (rmfiorg):

Advert in Radio Engineering June 1929tbn_duovac_re_629.png
Advert in Radio Engineering October 1929tbn_duovac_re_1029.png
Advert in Radio Engineering September 1929tbn_duovac_re929.png
Advert in Radio Engineering December 1929tbn_duovac_re1229.png
Advert QST Dec 1930tbn_usa_duovac_advert_1930.png
Radio Retailer and Jobber page 6, July 1929tbn_duovac_radio_retailer_jobber_july_1929_p6.png
Radio Retailer and Jobber page 7, July 1929tbn_duovac_radio_retailer_jobber_july_1929_p7.png


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