The 7705 SAR-A has two variants with fixed physical configurations. One variant supports both Ethernet and T1/E1 ports. The variant that supports T1/E1 ports includes eight RJ-45 T1/E1 ports. All ports must be configured as either T1 or E1 ports; a mix of T1 and E1 ports is not allowed.
DS1 (T1) ports on the chassis can be configured for either B8ZS (bipolar with eight-zero substitution) zero code suppression or AMI (alternate mark inversion). B8ZS and AMI are line coding techniques.