Thursday, November 02, 2006

To all you telecom people out there

Today, George Carlin on my daily George Carlin calendar, asks:
 
"I wonder when we pick up the telephone, does each of us get his own individual dial tone, or is there just one systemwide, master dial tone that each of us jumps on and off when we need it?"
 
Sounds like a stupid question, but it intrigues me. Know the answer?
 
 

2 comments:

Anonymous said...

That is a good question. I imagine there's a lot of younger people that don't even know what a dial tone is.

Anonymous said...

I was hesitant to answer this question because I might show my ignorance, but I am pretty certain that the answer is "It depends." For example, with our Vonage system the dial tone is created by the local router. No sound is sent over the cable modem line. All signaling is sent using SIP over IP and all tones are created or interpreted locally.

Your local PBX at work, somewhere in a closet, most likely creates its own dial tone as well, unless it is a Key system, in which case the tone is generated by the phone company.

If you use a traditional local telephone company the dial tone is created by the Central Office switch.

It used to be that everyone's dial tone was created by the Central Office switch, so for a small city, you could describe it as one tone that we jump on and off of.

Wikipedia says, "Before modern electronic telephone switching systems came into use, dial tones were usually generated by electromechanical means; in the United States, the standard "city" dial tone consisted of a 600 Hz tone amplitude-modulated at 120 Hz. Some dial tones were simply adapted from 60 Hz AC line current."