In serial data transmission, how is data sent?

Data in serial transmission is sent one bit at a time over a single wire. This method of transmission allows for the sequential sending of bits, making it simpler and often more cost-effective than parallel transmission, where multiple bits are sent simultaneously across multiple wires. Serial transmission is commonly used in situations where longer distances or greater reliability are important, such as in consumer electronics and computer networking.

The advantages of sending data serially include reduced complexity in wiring and connections, as only one channel is needed, which can also minimize potential interference among signals. Serial communication can be slower in terms of bit-rate compared to parallel transmission, but advancements in technology, such as high-speed serial interfaces, have helped mitigate this limitation.

In contrast, other options describe different modes of data transmission. The first choice suggests sending several bits simultaneously, which aligns more with parallel transmission. The second option implies that all data is sent at once, which is not characteristic of serial communication. The fourth option refers to sending data in parallel format, which again does not apply to serial transmission. Thus, the definition of serial data transmission is accurately captured by the correct answer.