Abstract: In digital measurement of the amplitude and phase of a sinusoidal signal of known frequency by the least square error method, the sampling frequency and sample size are carefully selected to satisfy a certain relationship. Under these conditions, the measurements are simplified and accuracy improved. This technique of measuring a sinusoidal signal is applied to the detection of a load coil in a telephone subscriber's loop circuit. The magnitude and phase of the driving point impedance of the loop are measured through the use of a series of discrete sinusoidal stimulus signals of predetermined frequencies and a digital signal processing technique.

Abstract: A frame synchronization detection system which enables frame synchronization and synchronizing pulses to be provided from at least two formats of DS1 TDM signals, specifically the D4 and extended superframe Fe formats. A first search logic circuit provides an output indicating the onset of a maintenance mode of frame detection when either Fe or D4 patterns are decoded. For the D4 pattern an alternate pattern is decoded and the first search circuit enters the maintenance mode only after both alternate D4 framing patterns are decoded. A second search logic circuit enables the decoding of a subsequent sequence and detection of framing, thereby reducing the probability of false framing. A frame counter which is synchronized upon the detection of a valid framing pattern by the first search circuit continues to supply frame sync pulses until an error detector, which detects whether a predetermined ratio of invalid to valid framing bits occurs, resets the system back to the search mode.