Tektronix 2714 User Manual page 321

Appendix B: System Messages
MARKERS ARE OFF
NO LISTENER
NO SIGNAL FOUND ABOVE THRESHOLD
NO SIGNAL AT CENTER OF DISPLAY
Firmware/Hardware error. Contact service center if message
center or representative if message persists.
NOISE LEVEL LESS THAN 2DB
Measured system noise level is less than 2 dB above the 2714
noise floor. Noise power correction has been made by NOISE
NORM''D or C/N mode algorithms in the 2714.