1. The 2018 is a 0.08 MHz to 520 MHz synthesized signal generator providing calibrated output levels from 13 dBm to -127 dBm. 2019 is a 0.08 MHz to 1040 MHz synthesized signal generator similar to 2018 except that a frequency doubler circuit enables it to cover frequencies up to 1040 MHz with the same output level range. The output frequency of both 2018 and 2019 is phase locked to a frequency standard and can be set to a resolution of 10 Hz at frequencies up to 520 MHz and to a resolution of 20 Hz above 520 MHz (2019 only). 2. Both instruments can be frequency modulated or amplitude modulated from external or internal modulation sources. The internal modulation source provides five fixed modulation frequencies; re-selection of components within the instrument allows alternative frequencies to be set if required. 3. Calibrated output levels from -127 dBm to +13 dBm (0.2 yV to 2 V e.m.f.) in the c.w. and f.m. modes and up to +7 dBm (1 V e.m.f.) in the a.m. mode are provided. A choice of nine output level calibration units can be obtained on the front panel. The r.f. output level can be set to a resolution of 0.1 dB or better over the entire output voltage range and features a total cumulative accuracy of ±1 dB up to 520 MHz (±2 dB, 520 MHz - 1040 MHz). Protection against the accidental application of up to 50 W of reverse power is provided by a fast responding reed relay. 4. Front panel operation is carried out by direct entry of required settings via the keyboard. Microprocessor control ensures maximum flexibility and allows programming by the General Purpose Interface Bus (GPIB). This facility is offered as an optional accessory enabling the instrument to be used both as a manually operated bench instrument or as part of a fully automated test system. Facility is also made for the use of an external standard reference when this is preferred. 5. A second function mode of operation includes means of setting the GPIB address, selection of alternative r.f. level calibration units, access to various calibration routines and a facility to aid diagnostic fault finding.