Taken from the Herpstat 1 Instruction Manual:
http://www.spyderrobotics.com/produc...t12_manual.pdf

"Output Mode: (Heat (Dimming), Heat (Pulse), Cooling)
Note: When the Mode is changed all settings for the selected output will be set to the defaults.
Heat (Dimming) can adjust the voltage output to the heating device similar to a household dimmer. In most
cases this is the best performing mode of control.
Heat (Pulse) can provide varied lengths of pulsed power to the heating device. This method of control can help
avoid the audible hum on metal rack systems .
The Cooling mode is a non-proportional mode that applies power when the set temperature is breached. The
Cooling mode then powers off the output when the temp drops below the Swing setting."