slicerwizard provided this link for us back in April for us when the question arose :
News Release
Toronto Police Service
For immediate release
Tuesday February 14, 2006
Please note that there has been an addition to the agenda for the Board meeting which will take place tomorrow, Wednesday February 15.
At approximately 3:00 PM, Chief Blair will make a presentation to the Board regarding the Toronto Anti-Violence Intervention Strategy (TAVIS). This is a major new Service initiative designed to address the factors contributing to violence. Recently, TAVIS rapid deployment teams have been assigned across the city, successfully working in our neighbourhoods to ensure the safety of all residents of Toronto.
---
"It is a new provincially funded special project which has specially trained officers respond to high crime areas, based on community concerns, in joint operations (for the most part) with the CRU (Community Response Units).
Their call signs will often have an S in it, like TAV S2, for the reason that many of the officers are above PC in rank. So on a certain call you may have several PC's and several "supervisors" such as S1, S2, etc on the same call."