ORIGINAL: Charlie P.
One thing you do have to watch is that servos have three leads - positive, negative and modulated signel input. Some drive the signal input with a positive modulation shift and some drive the signal input with a negative shift. The two don't play nice together and the receiver has to be designed to work one or the other. Futaba and HiTec, for instance, are compatable negative servos. JR and Airtronics both use positive shift; though JR makes servos in both modulations. Not sure about Spektrum but I believe I heard they are negative shift.
Sorry to be blunt, and I know it was made with the intention to help, but for education purposes: that entire post is incorrect.
Pos/Neg shift has to do with coding the signal between the transmitter and reciever. It only effects 72mhz PPM (fm) systems and only deals with reciever choice.
Once that signal is decoded the signal that gets sent to the servos is the same, something between 1ms and 2ms, the length of that pulse determines where in the sweep the servo goes. 1.5ms is center, 1 is full left, 2ms is full right.