1942: Radioear Model 45

The 45 line of hearing aids is a marked improvement in hearing aid technology because it is not only one of Radioear's first portable, wearable vacuum tube hearing aids with their new crystal receiver, but also a diagnostic hearing aid.

The Model 45 Electronic Radioear consisted of five units:

The combined microphone amplifier, which picks up and amplifies the sound
The battery, which supplies the electrical energy required to operate the instrument
The battery cord, which provides the electrical connections between the battery and the microphone
The receiver cord, which electrically connects the receiver to the rest of the equipment
The receiver, which delivers the amplified sound to the ear

There are three different arrangements, depending on whether a crystal air conduction receiver, a magnetic air conduction, or a magnetic bone conduction receiver was used.

A picture of a Radioear 45 window display. Various notecards are placed around a central central poster that reads “Announcing the RADIOEAR Electronic 45”, the smaller cards advertise features like “Air or Bone Conduction”, “New Crystal Microphone” or “Vacuum Tube Service”.

“Display Announcing Model 45 Radioear". Radioear Corporation Records, 1900-1990, AIS.2023.21, Archives of Industrial Society, Archives & Special Collections, University of Pittsburgh Library System, Box 47, Folder 3.

“Radioear 45”. Radioear Corporation Records, 1900-1990, AIS.2023.21, Archives of Industrial Society, Archives & Special Collections, University of Pittsburgh Library System, Box 22.

Kaple, Dan. Scanning consultation at Thomas Blvd. 28 November 2025.

A Portable Vacuum Tube Hearing Aid

The vacuum tube–based Radioear 45 is one of the few truly portable hearing aids of its kind, largely because vacuum tubes had significant limitations.

Although tubes offered better sound quality than carbon amplifiers, they were delicate, consumed a great deal of power, and became dangerously hot during extended use.

Soon after the development of micro-vacuum tubes, the invention of the transistor transformed hearing-aid design. Fully electronic aids could finally function reliably without the fragility, heat, and heavy power demands of vacuum tubes.

A close up image of a micro vacuum tube, it is shaped like a clear glass cylinder with a grey metal cylinder inside of it. 5 metal wires come out of the bottom of the cylinder.

A micro vacuum tube; note how much more condensed it is compared to the Vacuum tubes in the Radioear Executive

Crystal Receiver Design

rf, Mister. The CK512AX Is a Filament Type Subminiature Pentode Designed Primarily for Use in Resistance Coupled Audio Frequency and Direct Coupled Amplifiers., 8 Feb. 2023,

The Radioear 45 featured a new "capsule type" crystal element (patent pending at the time) that was more durable than traditional crystal receivers. The capsule design made replacement easy and cost-effective. Users could swap in a new capsule rather than replacing the entire receiver. They could also switch between crystal and magnetic receivers without changing the entire instrument, they could simply swap the cords.

The new receivers delivered superior tone quality, especially for high frequencies, despite being extremely small. Additionally, instead of housing the choke coil or transformer in the microphone case (standard practice), Radioear placed it at the lower end of the battery extension cord. This made the microphone smaller and lighter to wear.

An image of the carbon Radiear 45. Unlike the vacuum tube variant the microphone was a large disc separate from the main body.

“First Hermetically sealed amplifier -- a Radioear first". Radioear Corporation Records, 1900-1990, AIS.2023.21, Archives of Industrial Society, Archives & Special Collections, University of Pittsburgh Library System, Box 40, Folder 11.

Serving Diverse Hearing Needs

The design also featured an optional tiny booster plate that attached to the battery plug. This could significantly increase power for severe hearing loss cases.

Users with advanced hearing difficulties and those with milder loss could use the same instrument.

The body of the device also held a volume dial/power switch and a tone control lever; the tone lever could be adjusted to focus on high tones, low tones, or a neutral balance.

This tonal lever is intended to be shifted according to the needs of the user. Generally, shifting to higher tones made speech recognition easier in loud environments.

Wearing the Device

The Radioear's small size allowed users to wear it discreetly, a significant advancement for its time.

The manual stated that for women, the microphone unit could be attached to the top of a slip or other undergarment, with the battery worn at the side or attached to the leg, making it possible to completely conceal the device beneath clothing.

For men, a leather battery case could be fitted over the belt, while the microphone was tucked into a vest or coat pocket. Many men chose to position both the microphone and battery under the shirt, supported by light webbing.

Users were cautioned to keep metal objects (pencils, pens, jewelry, or clips) away from the microphone, as contact could cause disruptive noise. The microphone needed to be positioned securely to minimize movement.

Moisture protection was essential: rubber, rubberized fabric, or oiled silk shields were used to create barriers between the units and skin or clothing. Perspiration could damage both the battery and the microphone amplifier unit.

The Selex-A-Phone

Radioear suppliers tuned the Model 45 using the Radioear Selex-A-Phone.

The Selex-A-Phone fitting session was compared to an eye exam to help customers get acquainted with the process. The instrument simulated different hearing aid intensities so customers could actively participate in selecting what sounded best to their ears.

One particularly thoughtful detail reveals Radioear's human-centered approach: internal documentation encouraged customers to bring a parent or family member to the fitting. The reasoning was that testing with a familiar voice would yield more reliable results, as customers would naturally attune to voices they knew and loved.

A magazine spread advertising the Selex-A-Phone and Radioear Masterpiece. The spread lists various advantages to the Radioear Masterpiece such as the “Telephone Feature” or “New Waterproof cords”

An Advertisement for the Selex-A-Phone

The Radioear 45 cost $151 in 1945 or $2,755 in 2025, which is on the lower end of today's modern price range for a prescriptive hearing aid.

“Fitted with the Selex-A-Phone”. Radioear Corporation Records, 1900-1990, AIS.2023.21, Archives of Industrial Society, Archives & Special Collections, University of Pittsburgh Library System, Box 40, Folder 10.

The microphone and amplifier were built into the main body of the Radioear 45 with an external cable that would hook onto an A or B battery.

An A battery.

An image of a B battery, it is rectangular much wider than the A battery and has 3 connection points on its top.

A B battery; note how much wider it is in comparison to the A battery.

Julo. “Eveready #742 1½ Volts, Portable “A” Battery for 1.4 Volt Receivers,” Https://Commons.wikimedia.org/Wiki/File:A_battery_(Eveready_-742).Jpg, 30 Jan. 2008. Accessed 9 Dec. 2025.

Whitepines. Eveready #762-S 45 Volts, Radio “B” Battery (Portable Size), 4 Mar. 2014, commons.wikimedia.org/wiki/File:B_battery_%28Eveready_-762-S%29.jpg. Accessed 9 Dec. 2025.