82.1 Discrete-Time Signals Time-Domain Representation Unit of sampling frequency is cycles per second, or hertz(Hz), if T is in seconds Whether or not the sequence xn has been obtained by sampling, the quantity xn is called the n-th sample of the sequence Rxn is a real sequence, if the n-th sample xn is real for all values of n Otherwise xn is a complex sequence§2.1 Discrete-Time Signals: Time-Domain Representation • Unit of sampling frequency is cycles per second, or hertz (Hz), if T is in seconds • Whether or not the sequence {x[n]} has been obtained by sampling, the quantity x[n] is called the n-th sample of the sequence • {x[n]} is a real sequence, if the n-th sample x[n] is real for all values of n • Otherwise, {x[n]} is a complex sequence