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S12 off:
S12 on:
The board positions of the DIL switches and a flow diagram for the settings is given in the
Maintenance Manual.
B.5.
PROJECTING ASPECTS
Each modem-circuit on the MLU is projected with the signalling group 16XX. In the
subsignalling group (XX) 7 bits (bits 0 to 6) are used to define the operation of the related
modem and 1 byte (byte 0) is used to define the highest possible communication speed for
that modem.
Bit 0 (leased line connection):
This bit indicates if the modem is used for a leased line connection.
0
The modem is used as V.24 / analogue convertor and two paths through the switching
network must be established: from the DLC-circuit to the V.24 interface of the MLU
circuit and from the analogue interface of the MLU circuit to the ATU-circuit. The MLU
circuit must be assigned to a modem pool. In this case the board must be assigned with
board type 33.
1
The modem is used for leased line connection and only one path through the switching
network has to be established: from the DLC-circuit to the V.24 interface of the MLU
circuit (the analogue interface of the MLU circuit is not used). The MLU circuit with the
modem and leased line is regarded a normal trunk line by the SOPHO-S. In this case the
board must be assigned with board type 22. A free MLU-circuit can be seized using a
normal trunk access code to a destination with a leased line connected via a modem.
Bit 1 (constant carrier):
This bit indicates if the modem expects a constant carrier on the leased line.
0
The MLU regards a carrier signal on the line (indicated by the DCD signal from the
modem) as an incoming seizure of the leased line. Because the modem cannot receive
any dial information from the trunk line `DDI' is not possible. The trunk line must be
related to a -digital- PLE where the incoming call is directed to.
84
With some modem types the activation of CT108 will initiate a
protocol between the DTE and the modem for dial information. In
the modem pool use this is not useful. Therefore a delayed CT108
operation is introduced. When a modem out of a pool is to be
inserted in the connection, first V.25 answer tone is sent to the
modem and after a time period CT108 is activated. The modem
detects the answer tone and the protocol is not initiated any more.
normal CT108 operation.
delayed CT108 operation.
only used with leased lines
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