Instruction manual

Designing and Planning an M2150 System
Access Control Design Guide 13
Determine whether this level of communications security is necessary. The decision may be based
on any history of network interruptions and whether the network architecture could accommodate two
network paths to SMS PCs.
The feature is not applicable to other NIC modules, such as the NIC-WI. Each NIC4 module requires
a separate IP address.
Note: Only one LAN chain needs to be defined in the SMS software. The main tab of the LAN
Chains Definition screen is used to specify the IP address settings for the primary NIC module. A
Secondary option enables the IP address settings to be specified for the secondary NIC module.
Both NIC modules must communicate with the same SMS PC.
Fall-Back Communications
The on-board RS232 port or a one-port RS232 module can be connected to a modem for fall-back
communications to an SMS PC. Fall-back communications is used if the database unit is fitted with a
NIC4 or NIC-WI module for normal communications to an SMS PC and an Ethernet communications
failure is detected. Again, the client should be consulted to determine whether this feature is needed.
Serial Communications with an SMS PC using an RS232-to-20mA converter
An external RS232-to-20mA converter can be connected between the PC's serial port and the COM
A (20mA) port on the first database unit in the chain. The converter is useful if you want to use
RS232 communications from the PC, but the PC is located more than 45ft (15m) from the database
unit.
If bi-directional communications is used (see below), an RS232-to-20mA converter can also be
connected to the COM B port of the last database unit in the chain.
If an RS232-to-20mA converter is used, the port settings for the first and/or last database unit in the
chain must be set as for "database units between first and last" (see Table 2-1).
Communications to a Serial Device
The database unit can communicate with a serial device, such as an ENVS (which would allow the
database unit to trigger video recordings at an ENVS without the need for a connection to the SMS
software). The built-in serial port can be used for this purpose, or if the port is already in use, an
optional one-port RS232 module can be used instead. Only one port in a database unit can connect
to a serial device.
Bi-directional Communications
A chain can use bi-directional communications, where both the first and last database units in the
chain are connected to different RS232 ports at an SMS PC. In the event that communication
through the primary port fails, the secondary port is used instead.
If you require the chain to use bi-directional communications, each database unit at either end of the
chain must use RS232 communications to the PC, or must connect via separate RS232-to-20mA
converters. It is allowable for one end to communicate via the on-board RS232 (COM C) port or a
one-port RS232 module (COM D), and the other to use an RS232-to-20mA converter connected to
COM A or COM B as appropriate.
The port used for bi-directional communications at the last database unit in the chain must have its
port usage set to "Bi-directional RS232 Comms" if there is a direct serial connection to the PC, or to
the same settings as for "database units between first and last" (see Table 2-1) if an RS232-to-20mA
converter is used.