What type of multivibrator is often used as a timer?

A monostable multivibrator is often used as a timer because it is designed to generate a single output pulse of a specific duration in response to a triggering input. When the trigger signal is applied, the multivibrator changes its output state temporarily and then returns to its stable state after the set time period, which is determined by the component values within the circuit, such as resistors and capacitors. This behavior makes it ideal for timing applications, such as generating time delays or creating pulse-width modulation signals.

In contrast, an astable multivibrator continuously oscillates between its high and low states without the need for an external trigger, which is suitable for generating clock pulses but not for precise timing. A bistable multivibrator has two stable states and is typically used in applications requiring memory or state storage, rather than timing. RC oscillators also generate oscillations but primarily serve as frequency generators rather than timers. Therefore, the ability of the monostable multivibrator to produce a defined time delay based on external components makes it the correct choice for timer applications.