the period of a bit, baud, or symbol is simply 1/(bit rate), 1/(baud rate) or 1/(symbol rate).
For example, if we were transmitting 9600 bits per second, what is the period of a bit?
It is 1
/9600 = 104.16 µsec. For 2400 baud = 1/2400 = 416.6 µsec; for 33.6 kbps =
/33,600 = 0.0297 µsec, or 29.7 nsec.
Digital Data Waveforms
Digital symbols may be represented in many different ways by electrical signals to facil-
itate data transmission. All these methods for representing (or coding) digital symbols
assign electrical parameter values to the digital symbols. In binary coding, of course,
these digital symbols are restricted to two states, space (0) and mark (1). The electrical
parameters used to code digital signals are levels (or amplitudes), transitions between
different levels, phases (normally 0
for binary coding), pulse duration, and fre-
quencies or a combination of these parameters. There is a variety of coding techniques for
different areas of application, and no particular technique has been found to be optimum
for all applications, considering such factors as implementing the coding technique in
hardware, type of transmission technique employed, decoding methods at the data sink
or receiver, and timing and synchronization requirements.
In this section we discuss several basic concepts of electrical coding of binary signals.
In the discussion reference is made to Figure 10.8, which graphically illustrates several
Digital data transmission waveforms.
The electrical parameters used to code digital signals are levels (or amplitudes), transitions between different levels, phases (normally 0 and 180 for binary coding), pulse duration, and fre- quencies or a combination of these parameters.