small values of the order of micro to milli volts varying with time

large values of electrical voltages like 220 volts

Very large values of electrical voltages like 5 KV

constant function of time like 3v

Analog or digital electrical signal

only analog electrical signal

constant electrical voltage

only digital electrical signal

the voltages are fixed at 0 and 5 V

the value of the signal varies continuously with time

the signal value is available every 1 second

the voltages are fixed at -5 V and 5 V

only amplitude modulated values

only frequency modulated values

only continuous values

only discrete stepwise values

Noise produced by whistles

Noise produced by sound

unwanted signals that are mixed up with messages

signals that are amplified for performance