Method of operation
2
gas-net
C1 and C2
Page 2-9
Re 1) Data connection via modem and telephone line or GSM wireless network
The data connection usually uses either the public or the company telephone
network. If a system is not connected to a line-bound telephone network, a con-
nection can be implemented via the GSM wireless network.
An external modem is connected to the COM2 interface of the
gas-net
device
for connection to the respective telephone network.
In order to check the access authorization of the center, the integrated RDT
manages the bus address, bus identifier and password of the center (
Center
identifier
). A login procedure is carried out during a call connection. If errors
occur during this procedure, each side is authorized to interrupt the connection
by ‘hanging up’ for in this case a faulty connection or an unauthorized access
can be assumed.
The remote center, however, is only linked via the integrated RDT during an
established telephone connection. If the transmission of attention telegrams has
been parameterized, the center will be spontaneously called and informed. For
this, the integrated RDT has to know the center’s telephone number.
Furthermore, it is possible to synchronize the internal device time via the inte-
grated RDT if there is a server reachable by telephone and providing the time
via telephone in accordance with a defined protocol. Should you be interested,
please consult Elster-Instromet systems to clarify the usability of this functional-
ity in your case.
Re 2) Serial direct connection (null-modem cable)
In case of a serial direct connection the RDT assumes a continuous connection,
i.e. a leased-line operation. The interface hardware is connected by a three-core
null-modem cable; control lines are therefore not supported. The RDT is always
online, so there is no connection set-up, no login procedure, and no connection
tear-down. Telegrams to DSfG Class B may arrive at the RDT at any time and
are processed there accordingly, i.e. they are answered by internal bus stations
or routed to the local DSfG bus. Attention telegrams from local entities are
spontaneously sent by the RDT via the leased line to the center directly after
their creation.
This operating mode is thus intended for applications for which a continuously
established serial direct connection is guaranteed.
