1. If ensemble and time averages of a random process are identical, the process is ergodic.
2. If ensemble and time average of a random process are not identical, the process is ergodic.
3. An ergodic process is stationary.
4. A stationary process is necessarily ergodic.

Assertion (A): An on off controller gives rise to oscillation of the output between two limits.

Reason (R): Location of a pair of poles on jω axis gives rise to self sustained oscillations in the output.

Assertion (A): Fourier series can also be written in exponential form.

Reason (R): sin (n ωt) and cos (n ωt) can be expressed as sum or difference of exponentials.