A timer-controlled doorbell device has been developed using two 555 timer ICs in monostable mode, combined with a relay driver and a control circuit.

The 555 timer IC is an integrated circuit ... This enables you to vary the length of the output pulse in monostable mode or the output frequency in the astable mode. ... 555 as Monostable.

Frequently, the 555 is used in astable mode to generate a continuous series of pulses, but you can also use the 555 to make a one-shot or monostable circuit. The 555 can source or sink 200 mA of ...

A designer and a senior engineer analyze a low-cost alternative for solid-state general-purpose impact sensing uses a standard piezoelectric device (PZT) an a 555 timer.