How to add a random noise to a signal in Simulink model?

I am modelling a normal basic electrical circuit in simulink. If I need to add any random noise at source end or the load end, how can I do it?

regards,

reddy.

[KALYAN ACHARJYA]

I dont know, whether there is any random noise generator function block or not. I can give some way out. Use Gaussian, Rayleigh, or Uniform noise generator and activate any one at a time, use switch (or gates).

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