Abstract: The same recording head or heads may be employed to record both an information signal and a synchronization word signal. Where at least two recording heads provide overlap intervals in the recording of the information signal, the synchronization word signal may be recorded in such overlap intervals. Upon playback, the synchronization word signal may be employed to control at least part of the reproduction of the information signal.

Abstract: Methods and apparatus for demodulating time modulated carriers employ four matched transistors grouped in two comparator pairs. A single constant current source is provided for all four transistors. Emitters of the four transistors are metallically interconnected with each other and with an output of the single constant current source, whereby one of the transistors switches off the other transistors without the use of a capacitive element between transistor pairs. A common threshold reference voltage is applied to one transistor in one comparator pair and to one transistor in the other comparator pair. First and second repetitive pulses, preferably in the form of negative-going ramps, are generated in response to alternate successive zero crossings of the time modulated carrier.

Abstract: A velocity error compensator for a multiple video head VTR in which velocity error compensation is provided for all the lines adjacent a head switch. Separate velocity error detectors are provided in auxiliary channels continuously connected to each respective video head. By providing a mechanical overlap of video heads on the tape velocity error signals are developed for all the lines adjacent a head switch. Depending on the type of velocity error detection employed, the mechanical overlap must be sufficient to provide either simultaneous horizontal sync pulses or both horizontal sync pulses and color bursts from the adjacent heads. Suitable switching is provided to continuously apply the correct velocity error signal to the main channel video signal which is to be corrected. The arrangement avoids banding that develops in multi-generation copies where a line adjacent a head switch is not velocity corrected.