Zenith "York" (ZP-90)Behind-the-Ear Hearing Aid The Zenith "York" (ZP-90) behind-the-ear hearing aid was manufactured by the hearing aid division of the Zenith Radio Corp in 1974. It was a 3-transistor hearing aid. Notice the microphone port (bottom center). This hearing aid used an electret microphone. |  | Click picture for larger view | | |   | | |
| Side view of the Zenith "York" showing how the battery door swings up. This hearing aid used a No. 675 battery. The volume control wheel is on the right side above the battery door. The 3-position lever (below the battery door) is likely the tone control. |  | Click picture for larger view | | | |
| Extreme close-up view of the bottom of the switch (top left) and the icons below it, presumably meaning "off", "half" and "full" tone. |  | Click picture for larger view | | | |
| Side view of the Zenith "York" showing its size.
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