Contained on an 8-bit ISA bus legacy card, Model DDS7pc ISA card generates simultaneous ACMOS/TTL and sine outputs up to 68 MHz in 0.04 Hz steps under software control. An external clock input allows multiple units to remain phase synchronous and allows user configured frequency ranges. The sine output is programmable via an on-board step attenuator in 4 dB steps up to 60 dB or 1 VRMS to 1mVRMS. Both C language source and object software are supplied for DOS and Linux with out-of-the-box operation. The software permits switching of the frequency in less than 1 ms. With the supplied source code, users can customize operation using the freely available gnu C compiler.