Abstract: An acquisition circuit in an improved phaselocked loop prevents cycle slipping by detecting and compensating an impending large phase difference between an independent incoming signal and a local comparison signal dependently related to a voltage controlled oscillator. A train of pulses is generated in progressively delayed phase relation with each cycle of the oscillator output signal. Additionally a threshold signal related to the independent signal is produced. In response to overlap of the threshold signal and individual ones of the pulses, a phase error signal is generated which controls a commutator to select individual ones of the pulses having a predetermined delay as the comparison signal, thereby generating a correcting control signal to phaselock the oscillator at a faster rate than the linear response time of a standard loop.

Abstract: Secondary surge protection means for equipment connected to transmission lines, for example line-powered amplifiers interconnecting T1 or T1C telephone lines, includes two diode bridges and a pair of surge diverters. One diode bridge has its cathode/anode nodes connected one to each conductor of an incoming transmission line. The other diode bridge is connected in like manner to an outgoing transmission line. Each surge diverter interconnects the anode/anode node of one bridge and the cathode/cathode node of the other bridge. When a surge on one line causes the voltage across one or other diverter to exceed a predetermined threshold, the diverter conducts, shunting the surge past the amplifier to dissipate in the other line. The two transmission lines may be coupled to the input and output, respectively, of one amplifier, or to the input of one amplifier and the output of a different, oppositely connected amplifier.

Abstract: A polarity-insensitive code converter in which blocks of binary digits are translated into multilevel words having either one mode or another mode so that each coded word of one block of binary digits is the inverse coded word of the block of inverse binary digits. Hence, the inversion of a code word during transmission results in the inversion of the recovered binary. With additional precoding and postcoding of the binary signal, polarity integrity of the original signal can always be restored.

Abstract: A digital repeater for the regeneration of partial-response signals having improved noise immunity which basically comprises an equalizer followed by a regenerator. A band limiting filter disposed between the equalizer and regenerator transforms the partial-response signal to a modified form having the same or fewer levels and concurrently reduces the total power of the noise interference. A second filter disposed after the regenerator and having an inverse transfer function replicates the partial-response signal at its output so that the repeater appears transparent to the transmission line.