The 700-200 Series snap-action and snap-throttle (modulating) hydraulic controls are combination gas valves, thermostatically operated by a remote temperature sensing bulb. Two types of temperature adjustment models are available. One type is a single capillary model with the temperature adjustment knob on the gas valve itself. The second type is the remote dial, dual capillary model designed for cabinet mounting. These have an 18" capillary from the valve to the sensing bulb and a 48" capillary between the bulb and the remote temperature adjustment knob.The snap-throttle type controls are factory-set to snap on at 50% of the appliance capacity. From this 50% rate, the control will modulate up to full input rate if the demand for heat is great enough (as sensed by the remote bulb). As the temperature increase is sensed by the remote bulb, the control throttles the input back down to the minimum rate and when the temperature requirement is satisfied, the control snaps "off". These controls combine a manual valve (gas cock), an automatic pilot safety valve, pressure regulator (optional by model) and a snap-acting or snap-throttle hydraulic operator for total temperature control. All models feature 3-position main gas outlets and pilot outlet, pilot gas filter, pilot adjustment key and automatic pilot valve. The automatic pilot valve is separate from the gas cock and provides gas shutoff in case of pilot outage. Excellent replacement for competitive gas valves. Models have a slotted safety magnet. Made in the USA.