The Hewlett-Packard Model 8656A is a synthesized signal generator with a carrier frequency range of 100 kHz to 990 MHz. Its output amplitude is leveled and calibrated from +13 to -127 dBm. AM and/or FM functions can be individually selected. The carrier frequency, output amplitude, and modulation functions can be remotely programmed via the Hewlett-Packard Interface Bus. The unique modular design and incorporated service features permit rapid and easy calibration and service.