"signals" - key terms from Wikipedia

acoustic signals
analog signals
analogue signals
apoptotic signals
audio signals
block signals
brain signals
control signals
corps of signals
digital signals
efferent signals
emg signals
flag signals
front turn signals
gps signals
gurkha signals
hd signals
multipath signals
neural signals
nonverbal signals
other signals
pain signals
q signals
radio signals
rear turn signals
repetitive signals
rgb signals
road signs and signals
royal corps of signals
secam signals
separate signals
sequential turn signals
signals
signals	intelligence
signals	regiment
signals	squadron
signals	vehicle
smoke signals
speech signals
time signals
traffic signals
transmitted signals
turn signals
tv signals
uhf signals
uhf tv signals
unwanted signals
visibility signals
vlf signals
weak signals