Can the 660 Frame Relay Tester send loop codes?

Yes. To send a loop code, do the following:

          Select Single Test mode.           Select the Line Bert test; then press Enter.           Press the blue #1 softkey (Loop Back).           Select Transmit Loop Up/Loop Down; then press Enter.

The loop code highlighted at the bottom of the display is the code that will be sent. Pressing Enter lets you select a different loop code.