Signal Corps-era radio component

Dubilier Mica Transmitting Condenser Battery

A compact but heavy eight-section capacitor bank whose reported 0.0072 microfarad, 12,000-volt AC rating closely matches period Signal Corps spark-transmitter design examples.

Review evidence Open questions

What The Evidence Supports

The strongest claim is not a named radio set. It is that this is a WWI Signal Corps-era high-voltage transmitting condenser battery, very likely for the closed/tank circuit of a spark transmitter.

  • Verified
    Period terminology: 1910s radio manuals used "condenser" for what is now called a capacitor.
  • Verified
    Transmitting use: the Signal Corps manual describes mica and glass condensers in radio transmitting circuits.
  • Verified
    Numerical match: the manual's worked example gives about 0.007 uF at 12,000 volts for a spark transmitter; this battery is reported as 0.0072 uF at 12,000 V.AC.
  • Inferred
    Function: the battery was probably the energy-storage condenser in a spark transmitter's closed oscillatory circuit.
  • Inferred
    Construction logic: the open wood and hard-rubber frame fits exposed high-voltage radio apparatus, but does not by itself identify the installation.
  • Unproven
    Exact apparatus: no source found here proves SCR-49, submarine detection, shipboard service, a coastal station, or another named system.

How Eight Sections Become 0.0072 uF

The reported aggregate value follows from a series-parallel arrangement, with center-tap jumpers tying the branches in two paired groups.

One branch

Two equal capacitors in series produce half the capacitance of one capacitor.

0.0036 uF / 2 = 0.0018 uF

Four branches

Four identical series branches in parallel add together.

4 x 0.0018 uF = 0.0072 uF
Series-parallel condenser battery diagram Four horizontal branches, each branch containing two capacitors in series, with center-tap jumpers between the first two branches and the lower two branches. A B 0.0036 0.0036 0.0036 0.0036 0.0036 0.0036 0.0036 0.0036 center-tap jumper center-tap jumper 4 x (two 0.0036 uF sections in series)

The reported aggregate value corresponds to four two-section series branches in parallel. The center-tap jumpers tie the upper two branch midpoints together and the lower two branch midpoints together; with equal sections, the aggregate value remains 0.0072 uF. These two jumpers are visible in the exterior lightbox photographs at the top of the page.

The reported 12,000 V.AC system rating is best treated as the marked aggregate working rating. It is lower than the ideal arithmetic sum of two 8,500 V units in series, which is normal for conservative high-voltage design.

Why Mica Was The Right Material

Dubilier's reputation came from using mica as a compact, stable dielectric for radio condensers at a time when Leyden jars were bulky and fragile.

foil outer layer mica dielectric mica dielectric foil outer layer

Dubilier's patent described alternating metal foil and mica layers held under pressure, an approach suited to compact high-voltage condensers.

  • Verified
    Signal Corps manual: oil or well-selected mica had small dielectric absorption, reducing heat-producing losses.
  • Verified
    Cooper Union history: Dubilier developed a mica-dielectric capacitor in the early wireless era.
  • Verified
    Period Dubilier article: a 1920 radio article says high-voltage mica condensers used series sections to divide potential.
  • Verified
    Patent record: Dubilier filed a condenser manufacturing patent on Oct. 30, 1918, describing pressed mica and foil construction.

Period Pages

Text pages 18-20 of Dubilier's The Wonderful Achievements of Radiotelegraphy in War and Peace give the period explanation for why mica replaced Leyden jars in high-voltage radio service.

Text page 18 of The Wonderful Achievements of Radiotelegraphy in War and Peace beginning Development of the Mica Condenser Page 18
Text page 18 begins the mica-condenser development narrative and describes Dubilier's early effort to replace fragile Leyden jars.
Text page 19 of The Wonderful Achievements of Radiotelegraphy in War and Peace describing mica and foil condenser construction Page 19
Text page 19 describes the mica-and-foil sections, insulating adhesive, wax filling, pressure plates, and terminal arrangement.
Text page 20 of The Wonderful Achievements of Radiotelegraphy in War and Peace explaining voltage subdivision and self-healing claims Page 20
Text page 20 explains voltage subdivision across many mica-and-foil surfaces and Dubilier's self-healing reliability claim.

Local archived copy: The Wonderful Achievements of Radiotelegraphy in War and Peace PDF.

The Collins Connection

John Jenkins of the SPARK Museum supplied an important lead: Dubilier's public 1909 Seattle wireless-telephone story sits inside an earlier Collins Wireless Telephone Company context.

Jenkins note

In a June 2, 2026 note, John Jenkins reported that William Dubilier worked as A. Frederick Collins's assistant as a youth, and that he has photographs of Collins and Dubilier working on both the Collins wireless telephone and rotating arc telephony apparatus.

Jenkins also reported that Collins sent Dubilier to Seattle for the Alaska-Yukon-Pacific Exposition demonstration, then told him not to return; Dubilier remained in Seattle and continued improving the wireless telephone while postal authorities were moving against the Collins/Continental wireless promotion.

In a June 3, 2026 follow-up, Jenkins supplied three Collins-related Dubilier photographs, including a dated March 12, 1910 image of Collins and Dubilier working with a rotating oscillation arc.

What published sources support

  • In 1908, Modern Electrics published "The Collins Wireless Telephone" by William Dubilier, identifying him as "Assistant to Mr. Collins."
  • In H. LaVerne Twining's 1909 Wireless Telegraphy and High Frequency Electricity, Dubilier's wireless-telephony chapter identifies him as Chief Electrician of the Collins Wireless Telephone Company.
  • The 1909 Alaska-Yukon-Pacific award appears in Collins company material as a gold medal to the Collins Wireless Telephone Company, not solely as an individual Dubilier award.
  • MOHAI's collection record identifies a "Dubilier Wireless Telephone, 1910" artifact, with the June 21, 1909 A-Y-P demonstration in its caption.
  • The ETHW-hosted 1910 Continental brochure includes a section headed "Collins Wireless Telephone Co." and identifies A. Frederick Collins as inventor of the wireless telephone and as Continental's technical director and consulting engineer.
  • Jenkins also reports that the A-Y-P gold medal later remained with Collins family descendants, a useful lead for provenance research.
Page 7 of the 1910 Continental brochure headed Collins Wireless Telephone Co. Source page
Continental's 1910 brochure prominently ties A. Frederick Collins to the wireless telephone enterprise in which Dubilier was working.
Collins and Dubilier working with a rotating oscillation arc, dated March 12, 1910 Rotating arc, 1910 William Dubilier with Virgil Collins at Atlantic City Atlantic City William Dubilier with unidentified women on a beach, likely Atlantic City Likely Atlantic City

This does not diminish Dubilier's later condenser work. It sharpens the chronology: before the 1918 Signal Corps condenser, Dubilier was already deeply involved in radiotelephony demonstrations, arc-transmitter work, and the transition from bulky Leyden-jar apparatus to compact mica condensers.

The Faradon-Dubilier Link

Ira Goldklang's Faradon lead checks out as a real condenser-history connection, but not as proof that F.R.P.S. means "Fellow of the Royal Photographic Society."

What is verified

  • Faradon was a Wireless Specialty Apparatus Company name used on high-voltage fixed transmitting condensers.
  • The shared "Patented June 12, 1917" date points to two Dubilier Condenser Co. electrical-condenser patents: US1229914A to Philip Dubilier and US1229915A to William Dubilier.
  • William Dubilier's US1229915A describes a high-tension condenser for oscillatory or high-frequency alternating circuits, using sectional construction and mica dielectric.
  • A 1920 Dubilier notice reported a final decree in its infringement suit against Wireless Specialty over US1229914A and US1229915A.

What it means

  • Pickard and Wireless Specialty were not merely adjacent condenser makers. Pickard's later WSA condenser patent, US1503765, explicitly describes itself as an improvement on Dubilier patent US1229914.
  • That supports a real technical and patent relationship between the Dubilier and Wireless Specialty/Faradon condenser lines.
  • It does not make this Signal Corps unit a Faradon product. Its nameplates identify Dubilier Condenser Co., New York.
  • It also does not solve F.R.P.S.; that marking remains unexplained on this plate.

There is also a later corporate link: in 1949, Cornell-Dubilier announced that it had purchased RCA's Faradon Capacitor Division, including the Faradon trademark, tools, equipment, designs, processes, and patent licenses. That is a postwar business connection, not evidence about the origin of this 1918 Signal Corps condenser.

Patent PDFs

These local patent PDFs document the mica/foil condenser construction and the June 12, 1917 patent date reflected in the condenser-patent trail.

US1345754A

Method of manufacturing condensers. William Dubilier's 1918 filing describes mica and foil sections, pressure, impregnation, and insulating compound.

Open local PDF Google Patents record

US1229915A

Electrical condenser. William Dubilier's high-tension condenser patent was issued June 12, 1917 and assigned to Dubilier Condenser Co.

Open local PDF Google Patents record

US1229914A

Electrical condenser. Philip Dubilier's companion condenser patent was issued June 12, 1917 and also assigned to Dubilier Condenser Co.

Open local PDF Google Patents record

Timeline Context

The reported plate date falls at the end of World War I, during a fast transition from spark-gap transmitters toward vacuum-tube transmitters.

Dubilier publishes "The Collins Wireless Telephone" in Modern Electrics, where he is identified as Collins's assistant.
Dubilier is identified as Chief Electrician of the Collins Wireless Telephone Company in a wireless-telephony chapter; Collins Wireless Telephone Company receives an A-Y-P Exposition gold medal for its wireless telephone exhibit.
Dubilier develops mica-dielectric condenser work during his early wireless period, according to Cooper Union's historical profile.
A Jenkins-supplied photograph shows Collins and Dubilier working with a rotating oscillation arc apparatus.
Postal inspectors move against Continental Wireless and related wireless-stock promotions. Published accounts later describe Collins and associates being prosecuted for mail fraud.
Owner-reported nameplate date for this Dubilier Signal Corps condenser section.
Dubilier files US1345754A for a method of manufacturing condensers using foil and mica layers under pressure.
World War I Armistice. This does not prove the unit's use, but it frames the date as late wartime production.
Dubilier publishes notice of a final decree in its infringement suit against Wireless Specialty Apparatus Company over the June 12, 1917 condenser patents.
The revised Signal Corps manual still documents spark transmitter condensers and gives a 0.007 uF at 12,000 volts design example.
Greenleaf Whittier Pickard's Wireless Specialty condenser patent US1503765 is issued and describes the invention as an improvement on Dubilier patent US1229914.
Cornell-Dubilier announces its purchase of RCA's Faradon Capacitor Division, making the former Faradon line a Cornell-Dubilier product line decades after this artifact was made.

What Remains Open

These are the claims that should stay out of a final museum label until a document, marking, or catalog page supports them.

  • Unproven
    F.R.P.S.: Ira Goldklang suggested "Fellow of the Royal Photographic Society" via Pickard and Wireless Specialty's Faradon condensers. Faradon, Pickard's Wireless Specialty role, and the Dubilier/WSA condenser-patent link are verified, but no source found here connects the Royal Photographic Society to this Dubilier Signal Corps label.
  • Unproven
    Order No. 130402: the number is owner-reported from the plate; no online procurement manifest was located.
  • Unproven
    Specific service: no evidence found for submarine detection, a particular ship, a coastal station, or a named field set.
  • Research lead
    NARA: Record Group 111 is the broad archival target for Office of the Chief Signal Officer records.
  • Research lead
    Faradon comparison: Wireless Specialty Apparatus Company sold high-voltage "Faradon" condensers and later patent records tie WSA condenser work back to Dubilier patents. The comparison is useful, but it does not override the Dubilier nameplates on this artifact.
  • Research lead
    Photos: high-resolution images of all nameplates, jumpers, and stamped marks may identify a depot, inspector, or catalog type.
  • Research lead
    Measurements: individual capacitance/leakage measurements could test whether all eight sections remain electrically similar.

Sources

Source statements were used narrowly. When the artifact itself supplied a value, that value is labeled as owner-reported.