EXFO FTB-800 Series for FTB-1 - Manual (Page 367)

Test Results
NetBlazer 357
Summary (ISDN PRI)

Frequency column displays the following information:
RX (MHz) indicates the monitored frequency of the input signal. The
following table lists the supported frequency monitoring range:
Offset (ppm) indicates the offset between the standard rate
specification and the rate of the input signal.
Max (+) Offset (ppm) indicates the offset between the standard rate
specification and the largest rate recorded from the received signal.
Max (-) Offset (ppm) indicates the offset between the standard rate
specification and the smallest rate recorded from the received signal.
Note: Values inside the standard range are presented on a green background
while the value outside are presented on a red background.
Interface Standard Rate Specification
DS1 1544000 ±140 ppm
E1 2048000 ±100 ppm