Page 80 - Electrical Engineering Dictionary

and p(t) is the baseband pulse shape (e.g., ful for photorefractive and optical multibeam
raised-cosine). See also low-pass signal. coupling.

basic impulse insulation level (BIL) a battery one or more cells connected so
measurement of the impulse withstand capa- as to produce energy.
bility of a piece of electric power equipment
based on its ability to withstand 50% of im- baud the signaling rate, or rate of state
pulses applied at the BIL voltage. transitions, on a communications medium.
One baud corresponds to one transition per
basic input–output system (BIOS) part second. It is often confused with the data
of a low-level operating system that directly transmission rate, measured in bits per sec-
controls input and output devices. ond.
Numerically, it is the reciprocal of the
basic lightning impulse level (BIL) the length (in seconds) of the shortest element
strength of insulation in terms of the with- in a signaling code. For very low-speed
stand voltage crest value using a standard modems (up to 1200 bit/s) the baud rate and
voltage level impulse. bit rate are usually identical. For example, at
9600 baud, each bit has a duration of 1/9600
basin of attraction the region in state seconds, or about 0.104 milliseconds.
space from which a dynamical system moves
Modems operating over analog telephone
asymptotically toward a particular attractor.
circuits are bandwidth limited to about 2500
baud; for higher user data speeds each tran-
basis function one of a set of functions
sition must establish one or more decod-
used in the transformation or representation
able states according to amplitude or phase
of some function of interest. A linear trans-
changes. Thus, if there are 16 possible states,
formation T of continuous functions is of the
each can encode 4 bits of user data and the
form
bit rate is 4 times the baud rate.
Z
+inf ty At high speeds, the reverse is true, with
y(s) = T {x(t)} = x(t)b(s, t) dt. run-length controlled codes needed to en-
−inf ty
sure reliable reception and clock recovery.
where b(s, t) is a basis function. For discrete For example FDDI uses a 4B/5B coding in
sequences T would be of the form which a “nibble” of 4 data bits is encoded
into 5 bits for transmission. A user data rate
+inf ty of 100 Mbit/s corresponds to transmission at
X
y[k]= T {x[n]} = x[n]b[k, n]. 125 Mbaud.
n=−inf ty
baud rate See baud.
The function to be transformed is projected
onto the basis function corresponding to the Baum–Welch algorithm the algorithm
specified value of the index variable s or k. used to learn from examples the parameters
y(s) is the inner product of x(t) and the basis of hidden Markov models. It is a special form
function b(s, t). For the Laplace transform of the EM algorithm.
b(s, t) = e −st , and for the Fourier trans-
form b(ω, t) = e −jωt . For the discrete-time Bayes envelope function given a the prior
j2πkn
Fourier transform b[k, n]= e N , and for distribution of a parameter 2 and a deci-
the Z-transform b[z, n]= z −n . sion function φ, the Bayes envelope function
ρ(F 2 ) is defined as
BaTiO 3 (barium titanate) a ferroelectric
crystalline material that is particularly use- ρ(F 2 ) = min φr(F 2 ,φ),

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2000 by CRC Press LLC