These benchtop muffle furnaces are available in two chamber sizes. Type F47900 (F5185-1 thru -3) offers 120 cubic inches of heating area. Type F48000 (F5185-5 thru -7) which provides 350 cubic inches of heating area; a ceramic shelf is included to double furnace load capacity (F5185-9). Open coil heating elements on both sides of chamber assure fast heat-up, with minimum temperature gradient. Maximum energy efficiency is achieved by surrounding the chamber with thermal-efficient ceramic insulation. The rear of the chamber incorporates a 0.38" (0.95 cm) diameter port for monitoring chamber temperature with independent measuring device. Built-in venting system removes undesirable contaminants and moisture; extends the life span of the element and unit. Four temperature controller models are available for each of the two chamber sizes. A1: Digital single set point control. A single display shows actual temperature or set point. B1: Digital single set point control with a single ramp to set point and a dwell. A single display shows actual temperature or set point. The furnaces that use this control also utilize a mechanical Over Temperature Protection relay. C1: Digital programmable control with one stored program of 8 segments. The furnaces that use this control also utilize a mechanical Over Temperature Protection relay. D1: Digital programmable control with 4 stored programs, 16 segments per program. The controller also includes RS232 communications. The furnaces that use this control also utilize a mechanical Over Temperature Protection relay. Door safety switch protects operator by removing power to the heating elements upon opening the door. Thermocouple break protection cuts power to the heating elements, prevents a thermocouple failure runaway condition. All units include a thermocouple, grounded three-wire cord, and plug. 120V (240V available). Operating Temp. : 212° to 2192°F (100° to 1200°C).