simplex- one way transmission.only transmission will takes place here.

duplex- two way transmission.

Both transmission and reception takes place.

2 types of duplex:

1)Half duplex

2)Full duplex

Half duplex:-

both transmission and reception takes place,bt nt at d same time.single channel is used .

Full duplex:-

both txn and recep...takes place simultaneously using 2 different channels. one for txn and other 4 reception.