beckoning
heliography
telegraphy
waft
wafture
communication
alarm
alarum
alert
all clear
animal communication
beam
bugle call
curfew
distress call
distress signal
dog-ear
drumbeat
electronic signal
high sign
indicator
input
input signal
number
output
output signal
phone number
radio beacon
radio beam
radiotelegraphic signal
recording
retreat
start
starting signal
storm signal
symbol
telegraphic signal
telephone number
ticktack
time signal
visual signal
warning signal
whistle
whistling
acetylcholine
apoptosis
autophagy
blocker
bronchodilator
co-stimulatory
cytotoxic
downstream
effector
heme
milieu
proteases
telephony
transduction
visiphone
signalling