What is Serial & Parallel?

Digital data is data stored as a pattern of 1s and 0s. Digital pictures, audio, video, animation, documents, and so forth, anything stored in the computer is stored as a pattern of 1s and 0s. Most of the cables we sell are designed to allow computers and equipment to send these 1s and 0s from one to the other. ASCII is one of the oldest codes in use that assigns a unique pattern of 1s and 0s to each letter of the alphabet. When translated to ASCII, our IEC has the following patterns:

I = 01001001
E = 01000101
C = 01000011

If a computer wanted to print “IEC”, it would send these codes of 1s and 0s to the printer and the printer would translate them back to the letters to print “IEC”.

There are two basic ways to send the 1s and 0s. One is “Serial” and the other is “Parallel”.


Serial Interface


Serial Communications is like a one-lane road, where the 1s and 0s are transmitted in single file. The speed of transmission is either referred to as the “BAUD” rate (RS232), or simply as “Bits Per Second” (Ethernet).


Parallel Interface


Parallel Communications is like a multilane expressway, where the 1s and 0s are transmitted side by side. 8 bit parallel, shown in the illustration, is somewhat common, but there is also a 16 bit parallel which would have 16 lanes (think of doubling the size of the illustration, letters would travel across in pairs instead of each).


Pros & Cons

Parallel has the potential of being faster. If you observe the illustrations, the IEC seems to get across the parallel faster then the serial. But Parallel requires more conductors to make the multilane expressway. It would be quite expensive to run a large multiconductor cable for a couple hundred feet and so serial is chosen for long distance runs. As a result, parallel circuits are designed to provide a low voltage but high speed signal. So now it isn’t only expensive to run parallel a great distance but in many cases the signal is too weak so it won’t even work. Serial may seem slower, but it’s usually cheaper to boost the speed then it is to make more lanes. 100Base-T is a serial interface that transmits 100 million bits each second, and it’s still not the fastest. Fiber optic can go just about ten to one hundred times faster still. But imagine what it would be like to bundle eight fiber cables to allow for a parallel type of interface, you can see how expensive that would be and how much more practical it is to do serial and use the single cable. Of course, some interfaces are bi-directional or two way interfaces. Click here to see a better explanation of “Simplex”, “Half-Duplex”, and “Full-Duplex”.