Reply-Code Alpha

Reply-Code Alpha is a signal that Algalon the Observer could send to the Titans, signaling all is well on Azeroth. According to the Archivum Console of Ulduar, Reply-Code Alpha is one of two possible reply signals following by planetary diagnostics after the arrival of Algalon. The chance of Algalon sending such a signal is nearly 0%.

This item starts the quest.

Source
This item can be found inside Gift of the Observer after defeating Algalon the Observer in the 10-man version of Ulduar.