Tenma 72-10175 User Manual page 43

Set the Channel Bandwidth Limit
The oscilloscope is set to full bandwidth and will pass the high frequency component in
the signal if the "BW Limit" was turned off.
The oscilloscope will reject the frequency component higher than 20MHz if the "BW
Limit" was turned on.
When the "BW Limit" was turned on, a "B" sign will be displayed at the bottom of display
screen.
Set Math
Click "MATH" in Channel menu to set MATH channel.
The MATH Setup window