Abstract: A conveyor oven that preheats air for a combustion burner. A heat exchanger extracts heat from a heated surface of the oven to preheat the air. In one embodiment, the heated surface is a surface of a door and/or of a wall, particularly, a side wall that includes either an inlet or an outlet for the conveyor oven.

Abstract: A conveyor oven is provided that includes a conveyor assembly having an inlet section, and inner section and an outlet section. The conveyor assembly facilitates ease of removal by an enduser by allowing a single person to perform removal in a confined space.

Abstract: A self-calibrating threshold detector for use with receivers adapted to receive an incoming transmitted signal carrying a prescribed code. The detector comprises a single demodulating channel which includes a mixer having one input receiving the incoming signal and another input receiving a local replica code. During a short time interval, an incorrect local code is applied to the mixer to incorrectly demodulate said incoming signal and to provide a reference level that calibrates the noise propagating through the channel. A sample-and-hold circuit is coupled to the channel for storing a sample of the reference level. During a relatively long time interval, the correct replica code provides an output level which ranges between the reference level and a maximum level that represents incoming signal presence and synchronism with the replica code. A summer subtracts the stored sample reference from said output level to provide a resultant difference signal indicative of the acquisition of the expected signal.