Advanced Configuration Features
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Horizon Compact Release 1.01.00 Wireless Ethernet Product User Manual – Volume 2
3.12 Horizon Redundancy
The Horizon system can be configured for redundancy using two physical options. One option allows for
two separate Horizon units, each with its own antenna, and each having the P1 Payload port connected
to a switch or router. This option is termed the “2-wire” approach, since there are 2 P1 Payload wires or
Ethernet cables connected to the local Ethernet switch.
The second option has two Horizon units fed from a single P1 Payload connection to a switch or router.
This option is termed the “single wire” or “1-wire” approach.
In either case, a management cable is connected from Horizon Compact to the Ethernet switch. In a 1-
wire redundancy configuration, there is one Management cable and in a 2-wire redundancy configuration
there are two Management cables. In a 1-wire redundancy configuration, the management port is
activated on P1 of the Secondary unit and P2 of the Primary unit. In a 2-wire redundancy configuration,
management is configured on P2 of both the Primary and Secondary units.
The 1-wire solution has two Horizon units mounted on a Power Switch Radio Mount (PSRM). The 2-wire
solution may be mounted on a PSRM, or have both Horizon units mounted on separate antenna systems.
When in standby mode, the radio transmitter is muted. If the Primary unit is active, then the transmitter on
the Secondary unit is muted. If the Secondary unit is active, then the transmitter on the Primary unit is
muted.
3.12.1 BNC Connector
The BNC connector on the side of the Horizon Compact serves a dual purpose. It can be configured as a
source for field strength measurements during antenna alignment, or configured to provide a redundancy
switch signal to a second Horizon Compact system mounted close by. For redundancy applications,
ensure that the BNC connector is not configured for the alignment feature by using the CLI command set
alignment off and press Enter.
When the Horizon system is configured for redundancy, a DC signal is presented at the BNC connector of
the unit normally carrying traffic. Since the BNC connectors on both units are interconnected, the DC
signal is passed to the stand-by unit. As long as the DC signal is present, then the stand-by radio is held
in a hot stand-by state. When the DC signal is removed (as a result of the unit normally carrying traffic
failing), then the stand-by radio becomes active, and takes over the traffic. After a redundancy switch,
once the first system is able to return to carrying traffic, a manual switch is required, via a CLI command,
to return the system to its original state.
The voltage level at the BNC port is 3.3 VDC. The current draw is less than one-half milliamp and based
on standard coaxial cable specifications (for example 49 ohms per 1000 ft for RG-59), the loss is
negligible for the coaxial cable and therefore there is no rational limit on coaxial cable length.
3.12.2 Primary and Secondary Horizon
Configuring redundancy requires that one of the Horizon units has to be configured as the “Primary” unit
and the other as the “Secondary” unit. The terms “primary” and “secondary” relate solely to the internal
functions of the Horizon units and have no relationship to which Horizon radio is in stand-by or which is
carrying traffic. Either primary or secondary units may be active or in stand-by. The “primary” radio
performs the redundancy controlling and switching functions. On power-up, the Horizon unit that is
configured as the primary instructs the secondary Horizon unit to attempt to create a link with its peer at
the far end. If successful, this link becomes the active link and the primary Horizon remains in a stand-by
state unless the secondary unit link fails and thus causes the primary radio to take over the traffic.
3.12.3 How and When Protection Switching Occurs
Protection switching is triggered as a result of massive data loss caused by link outage, power failure, or
hardware failure. Modem-to-modem communications occur constantly, whether or not Ethernet data is
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