Control of power is also an important consideration, particularly in high Watt density applications. Inexpensive on-off controls are frequently utilized, but they often result in wide excursions in the temperature of the working parts and the heaters which can significantly shorten their life. Thyristor power controls and other digital temperature controllers are valuable in that they effectively eliminate on-off cycling which substantially extends the life of high Watt density heaters, they come in many different sizes with many output and input choices. Thermocouple and RTD inputs are the most popular with a DC pulse output. DC pulse outputs allow the user to use larger relays to switch the heater load.