Abstract: An offset compensation circuit for compensating a DC offset which occurs in a circuit line including an A/D converter or an A/D and D/A converter in which not only the polarity bit of digital data but also information concerning the amplitude of an analog input signal are applied to an integrator to precisely compensate an offset voltage in a circuit line. The level of a proper offset compensation voltage is provided even when an input analog signal such as a music signal is absent, and when an A/D and D/A converter is provided which can perform both A/D conversion and D/A conversion the DC offset can be precisely compensated shortly after the change of the mode from D/A conversion to A/D conversion.

Abstract: An apparatus for recording and reproducing digital signals using a helical scan in which a drum of reduced diameter is employed without changing the tape format. Two heads are mounted on a drum at the same height in opposition to each other with a product of the diameter D of the drum and the wrap-around angle of the tape with respect to the rotary drum being constant while the speed of the drum is increased to a speed N times higher than a predetermined speed. One of the heads is mounted higher than the other by a distance of (1-1/N)P to provide a step, and the other head being is mounted at a position an angle behind the position at which the other head directly opposes the one of the heads, which angle is defined by: ##EQU1## where L is the track length in the tape format used when the rotary drum rotates at the predetermined rotational speed, .THETA. is the track angle, P is the track pitch, and C is a constant dependent on the drum diameter D and the wrap-around angle.

Abstract: A recording/reproducing apparatus for transferring both information signals and address signals from one tape to another. A first tape is reproduced while monitoring the reproduced signal for the presence of address signals. When an address signal is detected, recording of the reproduced signal on the second tape is halted, and a new address signal corresponding to the detected address signal is generated and recorded on the second tape.

Abstract: A method for recording digital data on a tape in such a manner that the recorded data will not cause misoperations of the reproducing apparatus due to an excessive error rate. A flag in received data is monitored. When the flag indicates that a block of data contains more errors than can be corrected in the reproducing apparatus upon reproduction, the data block is either replaced by null data or a previously received data block having an acceptable error rate, the choice being in accordance with an input mode instruction.