DT Etherlink IV User Manual- 25 -E1-1, E1-2, E1-3 and E1-4 mean synchronization from one of the input E1 stream. If the E1 stream,which serves as a clock, is lost, the device switches to another clock according to the priority level.INTERNAL means synchronization from an internal clock source. This clock source should be thelast one in the priority list (but in the absence of any other clock source, for example, when onlyEthernet data are transmitted, this source can be the primary and the only one).Switching between clock sources occurs within 100 ms, after loosing synchronization.3.2.2.3 Nx64 and RS-232/RS-485 InterfacesThe Etherlink product family can be equipped with a wide range of modular and exchangeabledaughtercards with different interfaces. In this manual we describe the most important three cards.The first card supports Nx64 interfaces (V.35, V.36, X.21, V.28), the second card supportsasynchronous RS-232 interfaces and the third supports asynchronous RS-485.Nx64 interfaces: V.35, Speed 64…8192 kbps V.36 (with termination), Speed 64…8192 kbps X.21 (with termination), Speed 64…8192 kbps V.28 (synchronous), Speed 64…192 kbpsInterface type is cable selected. You can use the command EXTRATE [N] (N=1…128) to set thedata rate (N*64 kbps).RS-232 interface: RS-232, Speed 1200-256000 bps number of data bits: 5…8 number of stop bits:1, 1.5 or 2 parity: odd/even/odd/mark/spaceYou can use the command EXTRATE [N] to set the baud rate (N is baudrate, for instance 9600).The command RSFORMAT [format] is used to set the data format (example of format: 8N1).RS-485 interface: RS485, Speed 1200-256000 bps number of data bits: 5…8 number of stop bits:1, 1.5 or 2 parity: odd/even/odd/mark/spaceYou can use the command EXTRATE [N] to set the baud rate (N is baudrate, for instance 9600).The command RSFORMAT [format] is used to set the data format (example of format: 8N1). TheRS485 interface supports half- and full-duplex operation configurable by the command RSDUPLEX[F/H].3.2.2.3.1 Nx64 Clocking ModesNx64 clocking modes can be selected by using the command EXTCLOCK [SRC] [DIR]. The SRCargument sets one of 3 possible clock modes for the transmit and receive clocks (signal number 114(TX clock) and 115 (RX Clock)): NORMAL (DSL) both clocks are derived from the receiving DSL stream INT (internal) both clocks are generated from the internal generator signal TTC (external) clock for signal number 115 is derived from the terminal transmit clock input(signal number 113)The DIR argument sets the transmit clock direction: CO (codirectional): Transmit clock and transmit data have same directions, i.e. both are inputsto the modem at signal number 113 (clock) and 103 (data). In case of RX mode (see above)the whole TX path is clocked by this clock, while in other modes data coming to TX input(signal number 103) is put into FIFO using the clock from line 113 and get out from FIFO byclock defined by SRC.