Some examples of such low-cost serial buses include RS-232, SPI, I☬, UNI/O, 1-Wire and PCI Express. To reduce the number of pins in a package, many ICs use a serial bus to transfer data when speed is not important. Integrated circuits are more expensive when they have more pins. Many communication systems were generally designed to connect two integrated circuits on the same printed circuit board, connected by signal traces on that board (rather than external cables). Other such cables and ports, transmitting data one bit at a time, include Serial ATA, Serial SCSI, Ethernet cable plugged into Ethernet ports, the Display Data Channel using previously reserved pins of the VGA connector or the DVI port or the HDMI port. The cables that carry digital video are almost invariably serial-such as coax cable plugged into a HD-SDI port, a webcam plugged into a USB port or Firewire port, Ethernet cable connecting an IP camera to a Power over Ethernet port, FPD-Link, etc. Keyboard and mouse cables and ports are almost invariably serial-such as PS/2 port, Apple Desktop Bus and USB.
The cables that carry this data (other than "the" serial cable) and the computer ports they plug into are usually referred to with a more specific name, to reduce confusion. Practically all long-distance communication transmits data one bit at a time, rather than in parallel, because it reduces the cost of the cable.
Many serial communication systems were originally designed to transfer data over relatively large distances through some sort of data cable.
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