EXFO FTB-8510B Guia Del Usuario página 1175

Frequency: The Frequency alarm indicates if the received signal rate
meets (green) or not (red) the following rate specifications.
DS1
E1
2MHz
Frequency Analysis
Frequency (bps) displays the received signal rate in bps for DS1 and
E1 interfaces and in Hz for 2 MHz interface.
Frequency Offset displays the positive or negative frequency offset
between the standard rate specification and the rate from the received
signal. Frequency unit can be set to bps, or ppm for DS1/E1 and is set
to Hz for 2 MHz. The default setting is bps for DS1/E1 and Hz for 2 MHz.
SONET/SDH Application
Signal
1544000 ±15 bps (±9.2 ppm)
2048000 ±19 bps (±9.2 ppm)
2048000 ±19 Hz (±9.2 ppm)
Clock Synchronization
Rate specification
System Tab
525