Data Transmission

Direction of transmission may be:

1. Simplex: in 1 direction only  e.g. pc to printer
2. Half duplex: in both direction but not at the same time e.g. phone conversation
3. Full duplex:  in both direction simultaneously e.g.  broadband connection

Method may be:

1. Serial: sent 1 bit at a time over a single wire (easy to implement, suitable for long distance, but slower
2. Parallel: sent several bits of data at a time.  (suitable for short distance, faster, but difficult to synchronize data)

Synchronization may be:

1. Asynchronous: data is transferred in an agreed bit pattern having start and stop bits at both ends.
2. Synchronous: is continuous stream of data. Both sender and receiver are synchronized with each other.