Remote TARDIS Security System
This system is found on some Mark II and later TARDISes
and functions as a more primitive version of the SID.
It provides extra security by means of electronic eyes at the Main Doors and an internal scanner. If the beams from the electronic eyes are broken, an alarm is triggered. The system is also equipped with several tanks of nerve and stun gas, which can be triggered remotely or automatically whenever the beams are broken.