A keyer is a device for signaling by hand, by way of pressing one or more switches. Modern keyers typically have a large number of switches but not as many as a full-size keyboard; typically between four and fifty. A keyer differs from a keyboard in the sense that it lacks a traditional "board"; the keys are arranged in a cluster which is often held in the hand. An example of a very simple keyer is a single telegraph key which used for keying Morse code. In such a use, the term "to key" typically means to turn on and off a carrier wave. For example, it is said that one "keys the transmitter" by interrupting some stage of the amplification of a transmitter with a telegraph key.