NT6D70 SILC Line card Page 381 of 906Circuit Card Description and InstallationA logical terminal is any terminal that can communicate with the system overa DSL. It can be directly connected to the DSL through its own physicaltermination or be indirectly connected through a common physicaltermination.The length of a DSL depends on the specific terminal configuration and theDSL wire gauge; however, it should not exceed 1 km (3,280 ft).The SILC interface uses a four-conductor cable that provides a differentialTransmit and Receive pair for each DSL. The SILC has options to provide atotal of two watts of power on the Transmit or Receive leads, or no power atall. When this power is supplied from the S/T interface, the terminal devicesmust not draw more than the two watts of power. Any power requirementsbeyond this limit must be locally powered.Other functions of the SILC are:• support point-to-point and multi-point DSL terminal connections• execute instructions received from the MISP to configure and control theS/T interfaces• provide channel mapping between ISDN BRI format (2B+D) and systembus format• multiplex 4 D-channels onto one timeslot• perform activation and deactivation of DSLs• provide loopback control of DSLs• provide a reference clock to the clock controllerMicro Controller Unit (MCU)The Micro Controller Unit (MCU) coordinates and controls the operation ofthe SILC. It has internal memory, a reset and sanity timer, and a serial controlinterface.The memory consists of 32 K of EPROM which contains the SILC operatingprogram and 8 K of RAM used to store interface selection and other functionsconnected with call activities.
