Summoning device

The Summoning device was a piece of technology of Silurian design which was capable of calling forth other Silurians.

The machine was a hand sized device which, when activated, emitted a burst of communication that a Silurian could only hear. The Silurians gave one such device to one of their agents in order to recover a wounded and lost member of their race that was being hunted by Humans on the surface. (DW: Doctor Who and the Silurians)