| < Day Day Up > |
|
Each T1 carrier supports 24 voice channels. To support 60 voice channels, three T1 carriers are required. Two T1 carriers are not sufficient as they can support only 48 voice channels. However, when 3 T1 carriers are used, 12 voice channels remain free. It is a good practice to keep some spare capacity for future expendability.
You can see the datasheet of the IC 8880 from MITEL. This is a DTMF chip, and you can use the reference circuit given in the data sheet.
The IC 44233 generates PCM-coded speech.
The PSTN is based on circuit-switching. The switches contain (a) the line cards that interface with the subscriber equipment; and (b) processor-based hardware/software to switch the calls and establish a circuit between the two subscribers. Now the trend is to use packet switching for voice calls using the computer networking protocols. Switches that handle packet- switched voice are called the soft switches.
| < Day Day Up > |
|