The cheat codes are entered at the secured line box, the secured line is accessed by hitting the (ENTER) key on the keyboard. Most cheats spawn the item at center of the screen.

fortknox: adds $1000

keyholemaster: removes fog of war

ineedalltechnos: unlocks all techs and buildings

yeepeekaye: launches a massive explosion (Falling Star) at the center of the screen

bringoutthedead: spawns a civilian ambulance
coolihaveanewcar: spawns a CIA armored van
motherrussia: spawns a T80 tank
blackhawkdown: spawns a S.A.M. site

ymca: spawns a US cop
greenjelly: spawns a UK cop
swatatyourorders: spawns a S.W.A.T. team unit
coolimthepresident: spawns the US president
duckhunt: spawns a flying duck