Similar word to signalman:
caretaker, curator, custodian, detective, flagman, guard, keeper, lookout, observer, patrol, patrolman, picket, policeman, ranger, scout, security guard, security man, sentinel, sentry, signalman, spotter, spy, ward, warden, watch, watcher
caretaker, curator, custodian, detective, flagman, guard, keeper, lookout, observer, patrol, patrolman, picket, policeman, ranger, scout, security guard, security man, sentinel, sentry, signalman, spotter, spy, ward, warden, watch, watcher