Answer:
The police communicate in many ways, the most common way is to communicate via there two way radio transistors, many people think that it means only two people can communicate at one time, it doesn't it means they can listen and speak to the other people using that radio frequency. Another ternm for two way radio transister is a "walkie talkie".
Another way the police communicate is through hand communication to look at these heres a link
http://www.airsoftgent.be/dbase/hands.htm