There are three types of signals.
Buy
K% or D% Rise above Oversold.
Sell
K% or D% Falls below Overbought.
Two additional features.
Buy
Simple K% - D% Crossover
K% - D% Crossover in Oversold.
Sell
K% - D% Crossover in Overbought.
Simple K% - D% Crossover
The signals generated while the market is in Oversold / Overbought From my experience are more reliable.