Sampling

Sampling is the first step in converting the analog voice signal into digital pulse codes. The cross connect switches sample the analog line 8,000 times per second. There is a reason for this specific sampling frequency. The highest voice frequency reproduced by the phone system is 4,000 Hz. The sampling rate chosen for the analog to digital conversion process is designed to allow the phone system to reproduce the voice when it is converted from digital back to analog at the other end of the connection.