Servos and How They Are Wired
About 1991 or soon after, most of the major brands of servos became compatible with each other. When this happened, you could use any of these brands of servos with any brand of receiver, but you must be careful about the polarity of the wiring. Some brands of servos are really great for a particular use in a particular plane, and there are other companies that sell their servos with each different manufacturer's connector installed (you just have to ask for what you want).
You can mix Futaba servos with an Airtronics receiver, mix Hitec & JR servos with a FrSky receiver, etc. as long as you are careful about polarity. In Futaba, Hitec, and JR Radio servos, the servo and battery connections have the same polarity (+/-) and signal wiring, although the connectors are slightly different.
Now, having said all that, there are some newer digital servos that have a different pulse rate; the rate that control pulse signals are sent to the servo. Servo pulse rate (frequency) dictates how often a servo receives a new position command, typically 50Hz (every 20ms) for analog, while digital servos can handle 300Hz+ for faster response. Higher rates provide crisper, stronger holding power. The pulse width (1–2ms) determines the angle, while rate determines update speed. Recently some newer, super high-speed servos (often used in helicopters) use a shorter 760-microsecond pulse width (instead of the standard 1500µs) to allow for much higher update frequencies. So be careful when buying some of the fancy high-speed digital servos as you might find they're incompatible with your radio's receiver. I did.
The Airtronics “Z” Connector
Because Airtronics received so much bad press about the fact that their servos had reversed polarity (+/-), in December 1997, Airtronics started shipping servos with the optional “Z” connector that mostly matches the connector found on JR Radio or Hitec servos (or other brands). This means that if you have an Airtronics servo with one of the "Z" connectors, you won't have to switch (+) and (-) wires to use that servo with Futaba, Hitec, or JR, or other receivers.
If you want to switch the wires around, almost all the connectors have little tabs or pins that you can push with a small pin to remove the wires and push them back into the connector in the right place.
Wiring Diagrams
For Futaba, JR, Hitec, FrSky, Muizei, etc. servos (or servos with the Airtronics "Z" connector), use this diagram:
For Airtronics servos with the older, non-"Z" connector, follow this diagram:
If you are handy with a razor knife, you can get all the brands of connectors to fit each other. I usually cut off the little flat tab on the Futaba connector to get it to fit in a Hitec or Airtronics receiver. You can also cut off the three little 'teeth' on the Airtronics connector to get it to fit in another brand's receiver.
Some of the Airtronics servos have white colored wires for the 'Signal' wire, so it's easier to determine which black wire is (+). I can't emphasize this enough: if you connect Airtronics with the older (non-"Z" connector) to any other brand, you must reverse the (+) and (-) wires or you will burn out either the servo, receiver, or both.
I usually wrap all my servos that I've converted to Airtronics polarities with a little 'band' of bright blue tape to remind myself that the servo is setup as an Airtronics servo.
Analog vs. Digital Servos
Lots of people are now asking: “What is the difference between analog and digital servos?”
The motor of an analog servo receives a signal from the servo amplifier (inside the servo) at 30 times a second. This pulsing signal tells the servo motor when to start rotating and which way to rotate. Since it only happens 30 times a second, that's the minimum reaction time.
Digital servos use a higher frequency amplifier that sends a signal to the servo motor 300 times a second (or sometimes more on very fast servos, such as those used for helicopter tail rotors). Since this signal is received by a digital servo's motor more often, it is able to react much faster and hold its position better. This means the servo has better centering and considerably higher holding power.
This power comes at a cost, however, as digital servos tend to draw a lot more power from the on-board battery which means your battery just won't last as long.
Servo Motor Types
There are different types of servo motors available: cored, coreless, and brushless. You can read definitions of brushless, coreless, and cored servo motors in the glossary.
The Four Standard Connectors
Below are the four standard connectors used by the 'big four' radio manufacturers. Other manufacturers or third-party servo makers, such as FrSky, FlySky, and many newer servos, use the JR or Hitec standard. What to watch out for is that red is almost always positive (+), except Airtronics with the older non-Z connector. White, yellow, and orange are the signal wires for most of these types of servo.
Incidentally, if you want to make your own servo wiring without buying wire cables, you can just buy the 3-pin Du-Pont connectors from one of the electronics houses, such as AliExpress.com as they sell these in bulk for considerably less money, just be careful of the polarity of the wires!
Click any connector image to enlarge.