One of the biggest problems with Custom Chat mods presently is that the
sounds can't be heard unless the host of the game has the mod activated.
For instance everyone in the game may have downloaded the Robochat mod but
because the host doesn't have it activated nobody can hear the sounds.

This new system (known as the Deceiver Custom Chat System) involves tricking
Swat 3 into using sound mods that are placed into a special folder in the
MISSIONS directory. Any player that has this system installed will be able
to hear the sound mods in the game regardless of what mods the host has
selected. Simply put, if you have the sounds you will hear them.