The gyro-monotron (gyro-oscillator) is a single-cavity gyrotron that functions as an oscillator. A gyro-klystron is an amplifier that functions analogously to a klystron tube. Has two microwave cavities along the electron beam, an input cavity upstream to which the signal to be amplified is applied and an output cavity downstream from which the output is taken. A gyro-TWT is an amplifier that functions analogously to a travelling wave tube (TWT). It has a slow wave structure similar to a TWT paralleling the beam, with the input microwave signal applied to the upstream end and the amplified output signal taken from the downstream end. A gyro-BWO is an oscillator that functions analogously to a backward wave oscillator (BWO). It generates oscillations traveling in an opposite direction to the electron beam, which are output at the upstream end of the tube. A gyro-twystron is an amplifier that functions analogously to a twystron, a tube that combines a klystron and a TWT. Like a klystron it has an input cavity at the upstream end followed by buncher cavities to bunch the electrons, which are followed by a TWT type slow-wave structure which develops the amplified output signal. Like a TWT it has a wide bandwidth.