a light switch , on or off
Analog. They re-interpret physical movements to digital signals.
digital signals have two values. 0 and 1.
Digital signals are measured in bits per second (bps).
A microphone converts voice sound waves into electrical signals, which are then digitized by an analog-to-digital converter (ADC) to produce digital signals. These digital signals can then be processed and transmitted digitally.
Analogue signals are more vulnerable to error than digital signals. See the related question "Why digital signals are more noise free than analogue signals?" for more details.
To measure time between digital signals.
Digital signals are measured in bits per second (bps).
modem is the device that carries digital signals
it is an DAC (Digital to analogue converter
digital video camera
Hybrid signals are the combination of both analog and digital signals
Transforming analog signals to digital is known simply as analog to digital conversion, sometimes shortened to A-D conversion.