Apparatus for generating bi-phase coded characters

Abstract

Apparatus for generating bi-phase coded characters formed of a predetermined number of bi-phase signals representing binary bits '1' and 'O' having a constant relation between the phases at the beginning and end of each coded character regardless of the number of '1's and '0's included in the coded character. A source of binary bits supplies trains of serial bits corresponding to the coded characters, these serial bits being supplied to a bi-phase signal generator which is responsive to each bit for generating a respective bi-phase signal. A binary bit of predetermined sense is supplied in time coincidence with a selected one of the bits in each coded character; and this bit of predetermined sense is selectively inserted into the train of binary bits which is supplied to the bi-phase generator, thereby maintaining the constant relation between the phases at the beginning and end of the bi-phase coded character generated by the bi-phase signal generator. In a preferred embodiment, the coded characters are SMPTE time code characters, wherein a binary '1' bit is represented by a level transition at the beginning of the bit period and another level transition during that bit period, while the binary 'O' bit is represented by a level transition only at the beginning of the bit period. The bi-phase SMPTE time code character which is generated by the apparatus of this invention has a level transition at the beginning of the character which is of the same sense, or polarity, as the level transition which is provided at the end of that character.