1. Way of test: asynchronous and synchronous, dte and dce simulating. 2. Line code: 50b/sí½115.2kb/s, níß64k data is nrz code; 2m and 64k is hdb3 and ami code. 3. Clock testing: internal clock, receive clock or external clock 4. Interface circuit: v.24/rs232, x.21, v.35, v.36/rs449 can be select through menu. G.703 is set up 2m and 64k interface (64k has equidirectional, reverse interface). Characteristic of electrical apparatus matches itu-t input and output standard. 5. Output image: 215-1íó211-1íó29-1 pseudocode and 16bit artificial code 6. Error number: 0, single, 10-4, 10-3 7. Warning signal: ais, no signal, desynchronizing, error 8. Loop circuit time-lag test can be accurate as 0.01us 9. High capacity storage installed, over 6000 warning events can be stored. The stored information can be check or sent to pc or printed at any time. 10. Detect the test result of printing, manual or automatic printing in real time