KE LOGEM 928, Operation Manual

Page: 158 / 200

158 Operation Manual V.34 - Modems, Version 07/97
Chapter 7
During switched line operation the leased line is monitored constantly
with an integrated V.21 modem. This modem switches back to leased
line operation whenever it is able to transmit test data for the period
specified in register S63. Register S64 determines if the switched line
connection is terminated immediately after successful handshake on the
leased line. The max. number of switchings between leased line and
switched line is specified in the registers S65 and S66 to prevent perma-
nent switching between both connections. The LED A/O or ANS at the
front panel of the modems indicate the active connection procedure which
can be reported to the terminal equipment using the interface line M3
(incoming call, RI). Register S67 must be set to 1.
leased line dial backup active
M3 state active 1 inactive 0
indication A/O OFF blinks
or ANS
Tab.: Signaling of Line Connection
7.2.5 Leased Line Operation with Manual Dial Backup
Often 2 or 4 wire connections are implemented for data transmission
between local and remote computers. The modem establishes a switched
line connection if the leased line is disturbed or broken. This causes ad-
ditional line costs for the period the connection exists even if there is no
permanent data transfer.
The configuration with manual dial backup allows for user defined
establishment of a switched line connection even automatically or
whenever necessary by setting the V.24 control line S4/SEL thus facilitating
to set up a switched line connection by any DTE (SPC system, etc.).
öffentliches
Fernsprechnetz
HOST REMOTE
2-Draht-
Standleitung
S1 M2 D1 M5 D2 A/O Da/Te
LOGEM ®
928
S1 M2 D1 M5 D2 A/O Da/Te
LOGEM ®
928
Modem A
LOGEM 928
Modem B
LOGEM 928
Example A:
Two computers are connected via a 2 wire leased line. At failures on the
leased line a switched line connection is to be initiated and deactivated
manually using the Da/Te button on the modems front panel. Here modem
A calls modem B and data transmission between the computers is
Applications