hi
i hv a few problems in DSP can someone help me out with the way to go
about solving these problems:

Q1. whats the signal processing technique used for generation of 12
tone multisequence signal which is employed with push-button in
telephone set? also, whats the signal rejection technique used for
detection of this signal? how are these signals with push-button and a
human voice signal differently detected?


Q2. a band-limited continuous time signal is sampled at a rate of
7500Hz to ensure that there is no aliasing. the sampled signal is
windowed  generating a length 1250 sequence whose N-point DFT is then
computed:
a) what is the frequency resolution of DFT samples in Hz if N=1250?
b) what should be the values of N if a frequency resolution of 4.5Hz is
desired?


i wud b really grateful to ne1 who can help,
bye