Interlogix D19100SHR Series - Manual (Page 12)

Appendix
Automatic Switching Master
The automatic switching master feature gives the Self Healing Ring the capability of having two
redundant masters for the purpose of increasing fault tolerance Each master node may be connected
to individual host computers, or to a single host computer using a simple Y connection. Master nodes
may be located anywhere in the ring. In a redundant master configuration, one master will always be
in active mode while the other in standby mode. The active master will transmit and receive
RS232/485/422 data as usual while the master in standby mode will ignore data at at it’s data input
and it’s data output will be inactive and stay in tristate. If a master in active mode fails for any reason,
through automatic switching, the other master will enter active mode.
Loss-of-Data Detection
The loss-of-data detection feature increases fault tolerance in the RS232 data path from master to
host computer. This feature is only applicable when automatic switching master is enabled. A loss-of-
data jumper setting on the SHR sets a timeout on host data input inactivity. If the data input from the
host computer remains inactive for a set amount of time, a break in the data path is assumed. In this
case, a master in active mode will enter standby mode allowing the other master to become active.
Jabber Error Detection (Anti Streaming)
Used to detect an out-of-control RS232 data source. In some systems, an RS232 data source should
not continuously transmit for more than a specified amount of time. This feature is used to disable an
out-of-control data source by monitoring how long the CTS/RTS input line remains active. If it remains
active for more than the set amount of time, the RS232 input is gate off. Once an error occurs, the
error is latched. The only way it may be reset is by manually pressing the Anti-Streaming Reset button
or cycling power. In order for Jabber Error Detection to gate off the RS232 input, CTS/RTS must be
enabled.
Fail Relay
This solid-state relay is normally closed and only opens during a failure. On a slave, the fail state indi-
cates that lock cannot be achieved one or both of the fiber inputs. On a master, the fail state indicates
that lock cannot be achieved one or both of the fiber inputs, or that a fiber loop is reversed indicating a
failure somewhere in the ring. On both a master and slave, a Jabber Error is considered as a fail state
and opens the relay.
RTS/CTS
The RTS/CTS input is always looped around and drives the RTS/CTS output for use with computers
that require hardware flow control. The only exception to this is when Auto Switching Master is
enabled and the unit is in standby mode. In this case, the RTS/CTS RS232 output driver is tristate so
that a Y cable may be used to connect the output from both masters together. If a Y cable is not used,
the RTS/CTS input is used to gate RS232 input data. In this case, RS232 input data would be gated
off unless CTS/RTS is in the active state.
Master Relay
When Auto Switching Master is disabled, the solid-state relay is closed when the unit is configured as
a master and open when configured as a slave. By enabling Auto Switching Master, the unit becomes
a master. But in this case, the relay is closed when the unit is in active mode and open in standby
mode.