In a radio receiver with simple AGC

In force voltage analogy force is analogous to voltage and velocity to current. Just as , force/velocity = mechanical impedance.

Transfer function = .

Hence characteristic equation is .

For stability poles must be in left half plane. Zeros in left half plane lead to minimum phase shift.

At t = 0 the capacitor behaves as a short-circuit and output voltage is 0. At t = ? capacitor behaves as an open-circuit and V₀ = V_i.

. For the three systems the values of ??_n are 1.8, 2.5 and 2 respectively.

Hence values of T are 0.55, 0.4 and 0.5 respectively.

A signal (image) can interfere with a superheterodyne receiver if fits the following equation.

Image = Signal +/- 2 x I.F.

Which says that a signal has the capacity to interfere with a superhet receiver if its frequency is equal to the signal frequency (1200 kHz in our question) plus or minus twice the IF (455 kHz in our question).

So one possible image is: 1200 + ( 2 x 455 ) = 2110 kHz (possible).

And the other: 1200 - ( 2 x 455 ) = 290 kHz (not likely).