Within a
cathode-ray tube (CRT), the horizontal scan rate is how many times in a second that the
electron beam moves from the left side of the display to the right and back. The number of horizontal lines displayed per second can be roughly derived from this number multiplied by the vertical scan rate. The horizontal scan frequencies of a CRT include some intervals that occur during the vertical blanking interval, so the horizontal scan rate does not directly correlate to visible display lines unless the quantity of unseen lines are also known. The horizontal scan rate is one of the primary figures determining the
resolution capability of a CRT, since it is determined by how quickly the
electromagnetic deflection system can reverse the current flowing in the deflection coil in order to move the electron beam from one side of the display to the other. Reversing the
current more quickly requires higher
voltages, which require more expensive electrical components. In
analog television systems, the horizontal frequency is between 15.625 kHz and 15.750 kHz. == Other technologies ==