Solve : Telephone twist !!!?

Does anybody KNOW at what bitrate our voice is transmitted when we talk over the telephone?
If anybody know please help me....Sorry I did not see this earlier.
The human voice transmits sound caustically. The base frequency of a male voice is from 90 to 120 cps. But it is an analog structure. Some artifacts EXTEND above 10,000 cps. The level is normally about 60 decibels above the threshold of hearing in normal conditions.

(NOTRE the term Hertz is used now instead of CPS.)

To transmit the vice digitally, some kind of analog to digital converter is used. Many local telephone companies still used analog for all local telephone calls. For long distance digital transmission must be used. The has been the case fort a number of years now.
A common practice is to sample the voice using a rate of about 8000 cps which can reproduce sounds to about 4000 Hertz. After digital conversion it might bew transmitted at a rate of 64,000 bps. (Bits Per Second.)
For the exact values, ask a telephone engineer.
Sorry I can not find a specific reference that gives the exact answer. Some local Telcos may use different bit rates to meet needs is some areas.
This deference may help. Sort of.
http://www.tieline.com/Transports/POTSPSTN
Quote

Tieline POTS solutions provide 15kHz FM quality audio to broadcasters for just the cost of a regular phone call. In FACT, it sounds so good your listeners will find it difficult to tell the difference between POTS and either IP or ISDN connections!