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GEdney-9 Panel Exchange

” alt=”77th Street Central Office” width=”500″ height=”221″ /> 77th Street Central Office – Home of the GEdney-9 Panel Exchange

Recorded in 1977 by Ben Decibell – From  Evan Doorbell’s historic PhoneTrips library.

The GEdney-9 Panel Exchange was installed in New York Telephone’s “77th Street” Central office, located at 7703 3rd Avenue in Brooklyn.

GEdney-9 Panel Exchange

[youtube http://www.youtube.com/watch?v=tG14OkSd8j0&rel=0]

77th Street Central Office


Back in the day, the 77th Street Central office housed more than just the famous GEdney-9 Panel Exchange.


GEdney-9 Dial Tone

GEdney-9 was a wonderful panel exchange in New York City. Evan Doorbell’s PhoneTrips.com library has high quality recordings of calls dialed from this central office in the 1970’s. This next clip is a classic example of what is known as “Old City Dial Tone”. For dramatic effect, after about 50 seconds it transitions to another recording of dial tone, timing out; you can hear the panel revertive pulsing in the background as the call is connected to the permanent signal holding trunk. Ultimately, as the line is hung up, rich background sounds can be heard in this very high fidelity recording from Evan’s library:Can you hear how different from “Modern” dial tone it sounds? There’s a lot happening in the background. Here’s a side by side comparison of GEdney-9 dial tone versus “Modern” dial tone:

In the image below, “Modern” dial tone appears in the top trace and GEdney-9 dial tone on the bottom:

First of all, they’re based on different frequencies, so the the wavelengths are different. But look closely and notice that while the digitally-generated “Modern” tone waves are all perfectly smooth, GEdney-9’s all have slight bits of distortion; like snowflakes, no two are the same. That’s because the real GEdney-9 dial tone was not generated digitally; it came from large, rotating, motor-driven machinery. Background noise from the power supplies and the electromechanical switching equipment in constant operation added another, rich layer of character to the sound. You can really hear that influence of the background power supply noise when listening to the two side-by-side.

1920’s Tone Generator
1920s Ringing Machine

—from PanelSwitchman‘s collection on Flickr.

This is the type of rotating, electromechanical, tone generator and ringing machine that the GEdney-9 central office would have used.