For example, the use of sound, light or smoke. doves to the ancient sarotmai are not efficient because it is not possible to make a lot of news information, or even to give many details, but it is not secure.
As the use of sound, light, smoke or pigeons to communicate those ancient times. Rarely effective Because I can not give any more details. Or even give more details. However, it is not safe
Such as the use of smoke, sound, light, or pigeon communication the ancient times. Rarely effective. Due to the inability to detailed information as well. Or even give as many details, but it is unsafe.