Serial data transmission in which information can be transmitted in two
directions, but only one direction at a time, is called:

A.
Synchronized

B.
Full-duplex

C.
Simplex

D.
Half-duplex

Explanation:
The time required to switch transmission directions in a half-duplex
line is called the turnaround time.
* Answer simplex refers to communication that takes place in one direction only.
* Answer Synchronized is a distracter.
* Full-duplex can transmit and receive information in both
directions simultaneously. The transmissions can be asynchronous or
synchronous. In asynchronous transmission, a start bit is used to indicate
the beginning of transmission. The start bit is followed by data bits
and, then, by one or two stop bits to indicate the end of the transmission.
Since start and stop bits are sent with every unit of data, the actual
data transmission rate is lower since these overhead bits are used for
synchronization and do not carry information. In this mode, data is sent
only when it is available and the data is not transmitted continuously.
In synchronous transmission, the transmitter and receiver have synchronized
clocks and the data is sent in a continuous stream. The clocks
are synchronized by using transitions in the data and, therefore, start
and stop bits are not required for each unit of data sent.