U.S. Signal Corps EE-8 Field Telephone

The U.S. Signal Corps EE-8 field telephone was the backbone of American tactical battlefield communications from 1937 through the Vietnam War. Due to its rugged design, simple operation using batteries and a hand crank, and a range of 11 to 17 miles (17 to 27 kilometers), it became one of the most reliable and mass-produced military devices in American history.

• The TS-9 Handset: Equipped with a distinctive Push-to-Talk (PTT) butterfly switch. Pressing this closes the local battery circuit to power the microphone transmitter.
• The GN-38 Magneto Generator: A hand-operated dynamo that generates approximately 90 to 100 volts alternating current (AC) at a low frequency (~20 Hz). This voltage serves purely to ring the mechanical bell on the receiving telephone.
• The Local Battery (LB) Circuit: The voice connection does not use the energy from the hand crank. It operates entirely on two D-cell batteries. If the batteries are dead, you can still crank the handle to ring the other side, but they will not be able to hear your voice.
• Synthetic/Nylon: Models refurbished or built during the Korean War and the Vietnam War received synthetic cases and modified rubber cords to increase weather resistance.