bell
bell signal

busy
busy signal

calling
calling signal

danger
danger signal

directional
directional signal

distress
distress signal

engaged
line engaged signal

flashing
flashing signal

junction
junction signal

lamp
lamp signal

lantern
lantern signal

pilot
pilot signal

rocket
rocket signal

SC
Signal Corps

semaphore
semaphore signal

set
he set his watch by the time signal

signal
signal of distress

smoke
smoke signal

sound
sound signal

synchronization
synchronization signal

time
...the time signal

tower
signal tower

transmitting
transmitting television signal

whistle
whistle signal