Jittermodulator, intended for jitter generation up to 140 Mbit/s using the PF-4 Bit Error Measuring Set. Generates selectable jittered digital signals via the PF-4 Bit Error Measuring Set. Operates over a continuous frequency range spanning 1.5 to 45 MHz and 139.264 MHz when clocked externally. CCITT Rec. O.171 is met or improved on. Internal or external modulating signal. Remote control via the IEEE 488 Interface Bus.