Teleport homers produce a signal that can be locked onto by teleporting troops. If the template used by the teleporting Terminators to make a Deep Strike is centred on the model with the homer, then they won't scatter. Note that the homer only works for troops who are teleporting, not for troops entering play using jump packs, drop pods or other means of transport. Also note that the homer must be on the table at the start of the turn it is used.
Teleport Homer
Source: Codex: Space Marines, p. 35