RIGOL DM3068 - Manual (Page 95)

Chapter 2 Front Panel Operations RIGOL
User’s Guide for DM3068 2-53
 If the current reading exceeds the high or low limit, the vice display shows “HI
FAIL” or “LO FAIL” and the beeper sounds (beeper is on:  System 
Sound).
WARNING
The P/F signal from pins 1 and 9 of RS232 is not compatible with the
handshake signal (Carrier Detect and Ring Indicator) from standard
RS232.