1. Serial or parallel connection

1.1 Serial link

The serial link basically connects two devices and no more. It can be used between a digital sensor and a computer, or between a computer and a printer, for example. If the distance is short (< 100 m), the two devices are linked directly (via a 10-wire cable). If the distance exceeds 300 m, modems (modulator-demodulators) are required. In the example shown in figure 1 , it is assumed that transmission takes place via a telephone pair at a distance of between 300 and 1,000 m. Data characters are sent bit by bit, on 2 wires; all other wires are used for link management. During transmission, the parallel data is converted by the modem into a serial bit sequence; this information...