For the given 2-port network, the value of transfer impedance Z₂₁ in ohms is_______.

Two resistors with nominal resistance values $${R_1}$$ and $${R_2}$$ have additive uncertainties $$\Delta {R_1}$$ and $$\Delta {R_2},$$ respectively. When these resistances are connected in parallel, the standard deviation of the error in the equivalent resistance $$R$$ is

A stationary closed Lissajous pattern on an oscilloscope has $$3$$ horizontal tangencies and $$2$$ vertical tangencies for a horizontal input with frequency $$3$$ $$kHZ.$$ The frequency of the vertical input is

A $$10{\raise0.5ex\hbox{$\scriptstyle 1$} \kern-0.1em/\kern-0.15em \lower0.25ex\hbox{$\scriptstyle 2$}}$$ digit timer counter possesses a base clock of frequency $$100$$ $$MHz$$. When measuring a particular input, the reading obtained is the same in: (i) Frequency mode of operation with a gating time of one second and (ii) Period mode of operation (in the $$ \times \,\,\,10$$ ns scale). The frequency of the unknown input (reading obtained) in $$Hz$$ is _______.