Abstract: A digital signal reflection attenuation device is connected to a receiving end of a transmission line and contains a reflection attenuator connected between the signal line and the ground line, and also the signal line and the supply line. The attenuator clamps the voltage of digital signals between ground potential and the supply line voltage. Thus, even with a characteristic impedance mismatch between the transmission line and the receiver, accurate digital signals can be transmitted to the receiver.

Abstract: The specification discloses a circuit and method for detecting the presence and phase of a particular frequency in an input signal. The input signal is applied to the inputs of two linear multipliers and the other inputs of the multipliers are the inphase and quadrature phases of an interrogating signal produced by a fixed-frequency oscillator. The outputs of the multipliers are integrated over a selected time interval by two integrators and the outputs of the integrators are analyzed to determine the presence of the interrogating frequency in the input signal and to determine phase information regarding that portion of the input signal at the interrogation frequency relative to the interrogating signal.

Abstract: A lighting system for a welders helmet which includes a high intensity, high Kelvin temperature electric light source attached to the face shield for directing a high energy, high Kelvin temperature light beam forwardly of the viewing port, and an energizing circuit including an on-off switch interconnecting the light source to a source of electrical energy which deenergizes the light source where the welder's eyes are not protected by the face shield.