Voice Triangulation uses incoming radar waves from different stations to locate the source of a transmission. The approximate position is then displayed on the radar screen. The actual position calculated by Voice Triangulation can deviate a little from the actual origin of transmission, but it will be very close to the aircraft's position. That's how the controller can quickly see where the transmission is coming from even if it's outside of his airspace.
The Voice Triangulation feature draws a small circle around the origin of the transmission. This circle is then displayed differently according to the status of the plane. If the aircraft is squawking an emergency, the circle will indicate this by using an orange colour. Voice Triangulation can even track simultaneous transmissions coming from multiple directions.