The Perceptual Science Group of the Department of Brain and Cognitive Sciences at MIT does research in human vision, machine vision, human-computer interaction, and touch sensing for robotics. Both the Adelson Lab and the Rosenholtz Lab are part of the Computer Science and Artificial Intelligence Lab (CSAIL), located in the Stata Center.
The charming and talented Kitty Carlisle sings the “No Such Number” vacant level intercept tone from a #1-Step central office in Montreal Quebec in this raucous ringtone which also features vintage telephone sounds from the famous GEdney-9 electromechanical “Panel” central office.
This lively mashup ringtone combines ringback tone from the famous GEdney-9 panel exchange with the sounds of electromechanical revertive pulsing. Towards the end of the ringtone, a GEdney-9 busy signal joins in, alerting you that time left to answer your call is running out!
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.
God bless America, land that I love;
stand beside her, and guide her,
through the night with the light from above.
From the mountains, to the prairies,
to the ocean, white with foam,
God bless America, my home sweet home;
God bless America, my home, sweet home!