Air Brakes

Guys:

Need some help:

I stated to someone that I thought the Rio Grand had aair brakes from day one and that part of the reason for the mass purchase of cars in 1903-4 was because they needed to change from straight air to the new westinghouse system (type K) on hundreds of old 10,i5 and 20 ton cars. Then they asked for the difference between straight air and the westing house system and I faltered.I sort of know the answer but could use a little reinforcement

Can any one give a brief description of the straight air and westinhouse systems that I could give to someone with little RR knowledge.?

Frank