60 2000/3000 X-Series Oscilloscopes Service Guide 
3 Calibrating and Adjusting
 
Use 50Ω RG58AU or equivalent BNC cables when performing User Cal.
a For a 2-channel oscilloscope, connect a BNC tee to the equal length cables. 
Then connect a BNC(f)-to-BNC(f) (also called a barrel connector) to the tee 
as shown below.
Longer cable
To Channel 1
To Channel 2
to TRIG OUT