POTS (Plain Old Telephone Stuff)
The original phone system is also known as POTS (Plain Old Telephone Stuff). This is circuit switched and analog based. More formally known as the Public Switched Telephone Network (PSTN), it uses a copper pair to connect a building to the Central Office (CO). From there, the wire to the CO connects to local switch. The local switch connects to other switches, both local and long distance. Some long distance switches connect to other switches for carrying traffic overseas via cable or satellite. This makes the PSTN the largest network on the planet.
In a business office, a private circuit switch is known as a PBX (Private Branch eXchange). This allows the handling of internal calls without touching the PSTN. Frequently, a PBX is digitally based. This includes the PBX systems in hotels and motels.
You connect a computer to a remote network via POTS by using a device called a modem (short for modulator/de-modulator, which is what it does to the digital signal from your computer as it converts it to analog for transmission over phone lines, and then back to digital at the destination computer). The modem may be an internal modem ISA or PCI card that you install inside your computer, or an external modem that is a separate box you attach to your computer through a serial or USB cable.
The current maximum modem transmission speed is 56kb/sec. Note that this is ONLY the speed supported by the modem hardware. The actual transmission speed allowed by the telephone network is less than that generally around 53kb/sec if your phone lines are of very good quality.
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