KW_Counter,
Not always. It could actually damage the servo in some brands. It's best to make sure that the polarity of the servo matches the output of the receiver. Refer to the chart I posted above. For example, if you have a Futaba receiver then you will want to make sure that the servo you are using is wired like a Futaba servo on the chart above.

barracudahockey,
Even most older Airtronics will work, but usually the polarity on the wiring is reversed from most brands today.

Ken