Canon's EOS series of DSLRs usually have 3 kinds of switches:
1. There is a toggle switch under the mode dial on the right shoulder of the camera body, indicating on and off, which is mainly more common with Canon's entry DSLRs, such as the 400D.
2. There is a switch under the big toggle wheel on the back of the camera, which is mainly more common with mid-range and high-end DSLRs, such as the 5D 50D.
2.
3, in the body of the left shoulder mode dial, some film SLR usually use this way, such as EOS30 EOS50, etc..