Envelope is plotted above and below a
moving average using a specified percentage as a shift. The envelope indicator
is used to create signals for buying and selling, and the percentage to be used
for calculating the envelopes is specified by the user. This percentage should
depend on the volatility of the market (the higher the market volatility, the
higher the percentage should be). A sell signal is generated when the security
reaches the upper band whereas a buy signal is generated at the lower band.