Question

A modem from which communications occur in discrete units, and in which the start of a unit is signaled by a start bit at the front, and a stop bit at the back signals the end of the unit.

Answer 1

Asynchronous modem

Step-by-step explanation:

In an asynchronous modem, data is transmitted in an infrequent stream of small packets, in which a start bit at the front signals the start of a unit, and the end of the unit is signaled by a stop bit at the back.