A Digital Equipment Corporation VT520 terminal (1993) with its serial port connected to an Anderson Jacobson Model A 242 modem (1970s, see closeup) with a dial telephone handset plugged into its mating cups. To dial, the modem translates between the PC's ASCII characters (e.g. telephone number) and the tones or clicks recognized by the telephone network for dialing. The inset shows the connections between terminal, modem, and telephone (click image to enlarge).  Photos:  Frank da Cruz, 2011.