9.536 Protection-Switch-2-To-1

The Protection-Switch-2-To-1 logical device provides a completely software based solution for a 2:1 redundancy switch. The logical device monitors the fault states of a couple of devices, deriving from this the information whether to switch the (usually transmit-) chain.

As illustrated by the figure above, the redundancy switch reads up to five device fault variables for each chain and controls two switches. The latter not necessarily need to be waveguide switches as shown here. Any device may be configured to receive a command when the protection switch toggles the chain.

With a 2:1 redundancy, there is a dedicated spare chain which is placed into operation when one of the operative chains fails. A redundancy switch over takes place if these conditions become true at one time:

1. The spare chain states no fault.
2. There is a fault in at least one of the devices monitored for this chain for at least 'switchDelay' seconds.

When specifying the delay times, you should consider that the values become effective in steps of the IDLE time defined for the 'null' interface in the device setup. If the default value of 1000 msecs applies, all delays will be rounded up the next full second even if you specify fractions of a second.

The Protection-Switch-2-To-1 also is able to switch back to the original equipment in case of a a failure in the spare chain. Such a 'reverse redundancy switching' is performed under the following conditions:

1. The original chain is completely OK for at least 'recovDelay' seconds.
2. There is a fault in at least one of the devices monitored for the spare chain for at least 'switchDelay' seconds.

Device window pages

The following table shows which device window pages are available with this individual device type. Tool-bar functions not mentioned here are described at the general description of device windows .

• --- This page controls the operational parameters of the device.
• --- The faults page.
• --- The device info page.
• --- The maintenance page. The configuration parameters described below are set at this page.

Configuration parameters

At the maintenance page of the device window there are a couple of configuration parameter which must be set to interconnect the redundancy switch with the devices it shall monitor and control.

• Chain 1 --- A fault in one of the devices of Chain 1 is pending.
• Chain 2 --- A fault in one of the devices of Chain 2 is pending
• Spare --- A fault in one of the devices of Spare Chain is pending.
• Protection --- The protection switch raises (and latches) this fault flag if a switch over occurs. This fault maps to the 'switched' LED at the user interface. The flag is reset if you apply a 'RESET' command to the device (this command does nothing else for the Protection-Switch-1-To-1 device). Enable this fault if you want the switch over to be signaled as a latched fault.
• Switch configuration --- The switches are in an unknown or wrong position.

Variables defined by this device driver