Radio Controlled Toy Transmitters

Various radio controlled toy transmitters.
On the outside, radio controlled toy transmitters come in many shapes, sizes, and colors. They may have rocking switch controls, buttons, or dials. © J. James

Radio controlled toys communicate through radio signals. A transmitter is a (usually) hand-held device that sends radio signals to the radio receiver or circuit board in the RC vehicle to tell it what to do. The transmitter is also called a controller because it controls the movement and speed of the vehicle.

RC toy transmitters come in many shapes and sizes. They are usually made of hard plastic, have switches, buttons, or knobs, and have a wire or plastic-covered antenna. There may be lights to indicate when the transmitter is turned on. RC toy transmitters typically use AA, AAA, or 9-Volt batteries.

Open Up The Transmitter

Open RC toy transmitter
Usually a few screws are all that hold the transmitter body together. © J. James

Most radio controlled toy transmitters come in two main halves held together with screws. Simply remove all the screws. Some transmitters may be more tightly sealed with plastic tabs holding the two halves together. Be very careful not to break those plastic tabs if you want to be able to reassemble the transmitter.

Teardown Tip: Carefully separate the front and back of the transmitter, watching for loose pieces that may fall out. The switches for the controls may remain attached to the circuit board or they may fall loose, as the ones in the photograph did. Also, that piece of white plastic seen in the photo (left) came from a slot in the battery compartment. I encountered a similar piece in another transmitter. Don't lose it.

Watertight Transmitter Has More Layers

Toy submarine partially opened.
This toy submarine transmitter has all its electronics sealed good in case it gets dropped in the water. © J. James

The transmitter for a radio controlled toy that's intended to be used in or around water -- such as the submarine transmitter in the photograph -- may be more tightly sealed than other transmitters. After opening the two main halves, this transmitter had the circuit board inside another case. Silicon was used around all the openings for the wires exiting the enclosed circuit board.

Examine the Circuit Board

Circuit boards in RC toy transmitters.
The circuit boards inside radio controlled toy transmitters come in different shapes, sizes, and configurations to match the shape and style of controls on the transmitter. © J. James

The shape and size varies, but the circuit board is the


Teardown Tip:If wires have come loose, it may be necessary to carefully remove the board to get at the connections that need to be re-soldered. There may be a screw or two holding the board in place. Some boards are snapped or clipped in place. Be very careful when removing the board, especially if held in place with plastic clips. Even a tiny break at the edge can render the board unusable.

Components of Transmitter Circuit Board

Typical circuit board in RC toy transmitter.
On the circuit board of a radio controlled toy transmitter you'll find throttle and steering contacts, a radio crystal, antenna and battery connections. © J. Bear

Although they may vary in appearance and in placement, there are several common and easy to identify components on a typical RC toy transmitter circuit board. Some, such as the antenna (ANT), may be labeled right on the board.

As shown in the photograph, the main components are the switches or contacts for the throttle and steering (or other movement controls), antenna wire connection, battery wire connections, and the crystal. If you have fresh batteries but the transmitter doesn't appear to be working or is erratic, check those antenna and battery wire connections. A wire may have come loose.

Switches For Controlling Movement

Buttons and switches for throttle and steering.
The contacts for throttle and steering or other movements might be some kind of contact strips or little switches. © J. Bear

The transmitter for a radio controlled toy usually has some kind of rocking switch or push buttons to control movements such as speed (throttle) and turning (steering).

In the photograph you can see three different examples.

  • Upper left shows a rocking switch which alternates between two buttons on the circuit board.
  • The bottom image shows buttons (covered in plastic) which correspond to buttons on the face of the transmitter (see the submarine controller on the first page of this tour).
  • In the upper right image a rocking switch alternates between two metal strips which, when pressed, make contact on the board and complete a circuit that moves the RC toy in a prescribed manner.

Crystal on Circuit Board

Crystals in a pair of RC toy transmitters.
The crystal sets the radio frequency for communicating commands to the radio controlled toy. © J. James

Hobby-grade radio controlled vehicles use removable crystals which specify the radio frequency used to communicate between the transmitter and the vehicle. One crystal plugs into the receiver inside the vehicle. The other plugs into the transmitter. In toy-grade vehicles, the crystal is soldered to the circuit board inside the transmitter but it's easily identifiable by its shape. The specific frequency is usually etched on the top or side of the crystal. It might even be printed on the board, but not always.

For 27MHz RC toys, the specific frequency is usually 27.145 in the US. For 49MHz RC toys, 49.860 is common. However, radio controlled toys could use other frequencies. They may also have switches on both the transmitter and the vehicle which allow the user to select from up to 6 different channels within a certain frequency range. Both the vehicle and the transmitter must be using the exact same frequency in order to work properly.

If you have a couple of identical transmitters and aren't sure what frequency each one is, you can either try operating each of them with different frequency vehicles (easiest, as long as the vehicles are operational) or open up the transmitter and look at the frequency etched on the crystal.

I hope you've enjoyed this mini-tour inside a radio controlled toy transmitter. You may also enjoy looking inside a typical radio controlled toy truck.