Signals personnel are responsible for maintaining communications between units. In the days before electronic communications, this was achieved through the use of flags, heliographs (mirrors used to reflect sunlight) and dispatch riders and runners. With the advent of the telegraph, telephone and then radio, signals personnel became responsible for the operation and maintenance of this equipment. Although the Australian Army has been labouring for many years under the burden of Vietnam-era communications equipment, in recent years it has begun to introduce state of the art communications and computer equipment. Signals personnel are now also responsible for the Army's information technology resources. Signals personnel are known as "signallers" and, since their job requires much talking on various communications devices, they have been nicknamed "chooks".