voip:/etc/asterisk# modprobe ztdummy
voip:/etc/asterisk#  zttest
Opened pseudo zap interface, measuring accuracy...
-196.887207% -191.040039% -186.425781% -197.216797% -201.977539% -203.930664% -194.567871%
-189.477539% -194.555664% -195.727539% -201.196289% -191.345215% -189.562988% -198.071289% -202.746582%
-189.868164% -196.508789% -196.899414% -200.012207% -201.977539% -202.368164% -194.555664% -191.040039%
-202.770996% -200.402832% -198.449707% -197.290039% -190.258789% -201.586914% -199.633789% -198.461914%
-193.774414% -200.024414% -198.071289% -201.196289% -202.758789% -186.340332% -195.349121% -202.368164%
-198.852539% -199.243164% -193.774414%
--- Results after 42 passes ---
Best: 0.000000 -- Worst: -203.930664 -- Average: -196.870629
voip:/etc/asterisk#