Strowger Later Model Dial Potbelly

The Strowger dial was the first automatic dial telephone but the early versions of the dial had two flaws. Calling impulses were irregular because the person dialing could not dial the number at exactly the same speed and there were also premature releases of the switches because the dial could go backward. The telephone shown here is the only known example of the Strowger dial after patented improvements began in 1908. This particular Strowger dial telephone has been provided with the common dial and also a supplemental or controlling dial, forcing the dial in a forward direction, but not backward. With this arrangement both dials will rotate forward and when a subscriber releases them, only the inner (or common) dial will then rotate back to the normal position. This prevents any forcing or accelerating of the backward rotation of the calling dial, inasmuch as the outside or supplementary dial is always positively locked against back rotation. An arrangement of this character insures the proper transmission of the electrical impulses for operating the switches at the exchange or central station. The scan is from the U.S. patent office. The patent for this improvement was filed in 1908 and granted in 1915. Other scans are from original Strowger photos, catalogs and magazines.

Automatic Electric was created by the Strowger company to handle its manufacturing and marketing, and fully absorbed all the Strowger assets and patents in 1908. The "Strowger" name was tied specifically to Almon Strowger’s original patents. Almon Strowger was an undertaker in Kansas City who got upset because the operators there kept putting business through to his competition.

The earliest production models of the Potbelly (1901-05) featured a large, heavy dial with 11 holes (0-9 plus a "Long Distance" or "Operator" hole). These phones operated on a "three-wire" system. When you dialed, the pulses were sent over two wires to ground. On the very first 1901 models, dialing only connected you to the line; you often had to press a separate button on the base to actually "ring" the other party. These models were typically finished in high-polish nickel-plated brass. The transmitter (mouthpiece) was often a "long-back" style, and the receiver was a heavy, hard-rubber "pony" receiver.

By mid-decade (1906-08), AE began refining the dial mechanism to make it more reliable and user-friendly. They added the 'Sunburst' dial, named for the decorative "rays" or floral-like patterns stamped into the center of the metal finger wheel. This dial was slightly smaller and more robust than the original 11-digit version. During this stage, the dial was usually mounted halfway up the stem or on a slanted bracket attached to the "belly." AE also began experimenting with "two-wire" (metallic) signaling, which reduced the complexity of the telephone exchange wiring and improved call quality.

From 1908 to 1910, AE shifted to a "Mercedes" dial, as the Potbelly reached its final, most refined form before the design was simplified into the "Straight Shaft" candlestick. The Mercedes Dial: Introduced around 1908, this dial featured three distinct spokes in the center (resembling the Mercedes-Benz logo). This dial became the legendary standard for AE for decades. The 11th hole was largely phased out in favor of the standard 10-hole (0-9) dial we recognize today.

By 1910, manufacturing costs and the shift toward "Common Battery" (powering the phone from the central office rather than local batteries) led AE to move away from the expensive, ornate "Potbelly" casting.

Almon Brown Strowger was an American inventor for whom the Strowger switch, an electromechanical telephone exchange technology, is named.