 approximately a 10kHz repetition rate for the sawtooth horizontal deflection waveform).Using interlace, a pair of 202.5-line fields could be superimposed to become a sharper 405 line frame (with around 377 used for the actual image, and yet fewer visible within the screen bezel; in modern parlance, the standard would be "377i").The vertical scan frequency remained 50 Hz, but visible detail was noticeably improved.