E1 signals can carry the quality level value of the timing source via one of the Sa bits (Sa4 to Sa8) in a synchronization status message, as described in G.704, section 2.3.4. Choosing which Sa bit carries the SSM is user-configurable.
SSM over E1 is supported on the 7705 SAR-18 via the BITS ports. SSM via an E1 port is supported on the 16-port T1/E1 ASAP Adapter card, the 32-port T1/E1 ASAP Adapter card, and the 7705 SAR-A, 7705 SAR-M, and 7705 SAR-X chassis.