Pressurestats
Pressurestats can be thought of as a switch activated by pressure. When the pressure reached the predetermined level (Can be adjusted however is usually set at between 1.1 - 1.3 bars depending on machine and usage) the pressurestat cuts off, as such it turns off the element. It will then turn on the element when the pressure drops again.
The on and off cycle of the pressure stat will depend on the variance (different from brand to brand) and this process is called cycling.
All machines have either a pressurestat, thermostat or PID to control the element, however pressurestats still remain the most common choice.