Circulator:

Construction diagram:

Applications:

1. Circulator used as coupling element for reactance amplifier.
2. Circulator used as duplexing and phase lock injection element.
3. Circulator used primarily in radar and communication system.

Isolator:

Construction diagram:

Application:

1. Isolators are most widely used to protect high power RF sources.
2. Isolators are often used between the transmitter and the antenna is several communication systems and radar systems. They are also used on the output of signal generators.