The monitor has an 11.5-inch wide CRT (measured diagonally) with 90 degree deflection, etched to reduce glare, with a resolution of 350 horizontal lines and a 50 Hz refresh rate.[3][4][6] It uses TTL digital inputs through a 9-pin D-shell connector, being able to display at least three brightness levels, according to the different pin 6 and 7 signals.[7] It is also plugged into the female AC port on the IBM PC power supply, and thus did not have a power switch of its own.
The IBM 5151 uses the P39 phosphor type, producing a bright green monochrome image intended for displaying high-resolution text.[8][6] This phosphor has high persistence, which decreases display flicker but causes smearing when the image changes.[9][10]
