A callbox is a ter'angreal, a few copies of which exist.
A callbox is a small, gray cube that is carved with intricate patterns that seem to have no end.
Using saidar to channel Fire into a callbox causes the ter'angreal to draw in the other powers, as well as saidin. In this way, a male channeler can sense the callbox and hear and speak through it.
Morindin commented to himself, stating 'It was wonderful what you could learn with a callbox, especially in a world where there seemed to be only two others."
- See also: brilliant red rod