This Synthesised Programmable Arbitrary Waveform Generator uses a combination of direct digital synthesis and phase lock loop techniques to provide high performance and extensive facilities in a compact instrument. It can generate a wide variety of waveforms between 0·1mHz and 15MHz with high resolution and accuracy. Arbitrary waveforms may be defined with 12 bit vertical resolution and from 4 to 65536 horizontal points. In addition a number of standard waveforms are available including sine, square, triangle, ramp and pulse. Arbitrary waveforms may be replayed at a user specified waveform frequency or period, or the sample rate may be defined in terms of period or frequency. Extensive waveform editing features between defined start and end points are incorporated, including waveform insert, point edit, line draw, amplitude adjust and invert. More comprehensive features are available using the WaveCAD arbitrary waveform creation software supplied. WaveCAD is a powerful Windows-based design tool that enables the user to create waveforms from mathematical expressions, from combinations of other waveforms, freehand, or using a combination of all three techniques. Waveforms created in this way are downloaded via the RS232 or optional GPIB interface. Up to 50 waveforms may be stored with the length and name specified by the user. Waveforms may be strung together to form a sequence of up to four steps. Each waveform may have a user defined repeat count from 1 to 32768. All waveforms can be swept over their full frequency range at a rate variable between 30 milliseconds and 15 minutes. Sweep can be linear or logarithmic, single or continuous. Single sweeps can be triggered from the front panel, the trigger input, or the digital interfaces. A sweep marker is provided. Amplitude Modulation is available for all waveforms and is controlled from an external generator via the Ext VCA input. All waveforms are available as a Triggered Burst whereby each active edge of the trigger signal will produce one burst of the carrier. The number of cycles in the burst can be set between 1 and 1048575. The Gated mode turns the output signal On when the gating signal is true and Off when it is false. Both Triggered and Gated modes can be operated from the internal Trigger Generator (0.005Hz to 50kHz), from an external source (dc to 1MHz) or by a key press or remote command. The signals from the REF IN/OUT socket and the SYNC OUT socket can be used to phase lock two or more generators. This can be used to generate multi-phase waveforms or locked waveforms of different frequencies. The generator parameters are clearly displayed on a backlit LCD with 4 rows of 20 characters. Soft-keys and sub menus are used to guide the user through even the most complex functions. All parameters can be entered directly from the numeric keypad. Alternatively most parameters can be incremented or decremented using the rotary control. This system combines quick and easy numeric data entry with quasi-analogue adjustment when required. The generator has an RS-232 interface as standard which can be used for remote control of all of the instrument functions or for the down-loading of arbitrary waveforms. As well as operating as a conventional RS-232 interface, it can also be used in addressable mode whereby up to 32 instruments can be linked to one PC serial port as part of a TTi "ARC" system. Alternatively, a GPIB interface conforming to IEEE-488.2 is available as an option.