120A channel service unit (CSU) module connects to either a TN464E/F
or a TN767D/E DS1 circuit pack on 1 end. The other end connects
to the network interface smart jack. The 120A is powered from
the +5 VDC port carrier power supply and uses a maximum of 1.2
combination with the DS1 circuit pack, it provides the essential
functions of external CSUs. The TN464/767 and switch administration
support all framing and line coding options.
120A is small, a little larger than a wallet, is easier to install
than an external CSU, and does not require any option switch settings
or DS1 cable.
2 of the 120A CSU module (the 120A2) provides enhancements to
support the payload loopback function available when the ESF framing
format is selected.
700A loopback jack is controlled from the network side using the
data link provided by the ESF framing format. This provides a
loopback of data back to the network and operates as defined in
Clip and Cable.