1.385 Multi-Protection-Switch

The Multi-Protection-Switch logical device implements up to 16 N:1 redundancy control units for up to 32 devices / chains in one logical device. The assignment of chains to a certain redundancy control may be done by the operator 'on the fly' in the running system.

While originally developed as a modem / modulator redundancy controller, the Multi-Protection-Switch device may be used for other purposes as well. It only requires that:

• Each device or device chain monitored by the device must provide one fault flag signalling any malfunction of the device. The sat-nms logical devices Logical-Gate or Logical-Gate-3 may be used to combine multiple fault conditions to the summary fault of the device chain.
• There must be one ON/OFF switch which switches the device chain in place (ON) or to standby (OFF). With satellite modulators this is the TX-ON switch, that's the reason why this parameter is labeled TX-ON in the device.
• There may be a signal input switch, which specially for the redundant chains control the input signal processed by this chain.

Configuration

The relevant parameter IDs of each device / device chain controlled by the device must be configured at the device's setup page. Once a device chain has a 'txOnId' set, it appears as configured at the 'Group definition' page and may be assigned to a 'group'.

A 'group' in this context means a N:1 protection switch unit. A group may consist of 2 to 32 device chains, exactly one of them must be configured as a spare chain.

The 'Group definition' page lets you change the group assignment of each chain on the fly in the running system. You are strongly encouraged to set the global protection enable to OFF while you modify the chain configuration. Unwanted automated switching may be triggered due to new / partly configured chains coming into a group.

Operation

Each group acts as a independent N:1 protection switch. If enabled, it replaces a faulty device by the spare. The switchover process is as follows:

1. The faulty device is switched TX-OFF.
2. The input switch of the spare device is set to the same input as the switch of the faulty device was set (if input switch IDs are configured).
3. All settings of the faulty device are copied to the spare device. As the settings memorized in the device driver are used for this, copying works even if the faulty device if completely down.
4. The spare device is switched TX-ON. The redundancy switching is 'one way', the first fault that is recognized triggers a switchover, after this the protection switch has to be reset to enable it again. Resetting the protection before the fault condition has been cleared causes the switch to switchover again immediately.

Redundancy switch enabling

There are three levels of enabling the redundancy switch function of the device. First the primary page of the device window provides a global enable switch (at the very bottom of the page). Setting this to OFF inhibits any redundancy switching. The same page shows one enable switch for each group. Setting the enable parameter of a group to OFF inhibits the redundancy switching for this particular group. Then, at the 'Group definition' page, there is a enable switch for each individual device chain. By setting the enable switch of a device chain to OFF, you may exclude this chain from redundancy switching (This in fact masks the fault of this chain).

A fault of the spare device also inhibits redundancy switch for this protection switch. The Multi-Protection-Switch signals this as a fault.

Delay times

The protection switches are triggered by every fault condition, there is no delay / filtering forseen. If such a filtering is required to prevent short fault conditions from triggering a switchover, you may use the fault delay parameters in each individual device protected by the redundancy controller.

The Multi-Protection-Switch provides a 'tx on delay' which postpones the TX-ON command at the spare chain for some time (0..5000 msecs). This may be useful for devices which are busy for some time after parameter mirroring and therefore would ignore an immediate TX-ON command.

Input switch neutral position

For each group a input switch neutral position may defined at the setup page. If this switch position is not empty, the protection switch will change the input switch of a chain which caused a redundancy switch to neutral. The original switch position is remembered and will be restored when a 'RESET' is commanded for this protection switch. The redundant chain will be switched neutral with the 'RESET' command.

Using a neutral input switch position is helpful with setups using bi-directional modems. With a redundancy switchover not only the faulty chain is switched TX OFF, also the receive signal gets removed.

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 shows the actual state of each group and permits to reset or disable individual groups.
• --- This page shows the state of each device chain and lets you configure the group assignment for each chain.
• --- 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 parameters which must be set to interconnect the redundancy switch with the devices it shall monitor and control.

Variables defined by this device driver