The Logikey keyer by Idiom Press lists no less than ten "emulation options", or keyer timing modes. They are numbered "V0" through "V9", including three different Curtis A modes, three Accukeyer modes, and others. "V0" is the best timing I've ever used on a keyer. I don't know whether it's A, B, or other, but it's accurate, smooth, and feels right. Al W6LX/4