Teledyne 7 RU Chassis, Operation Manual, Page: 60 / 144

60 208528 REV M Operations Manual, 7RU SSPA Chassis
3.7 N+1 Operational Basics (single unit)
A single SSPA unit may be operated in N+1 mode in order to take advantage of the Auto
Gain Control features described in
Section 3.6.6.3 . In this case, each SSPA module within
the SSPA chassis is counted as a separate N+1 entity. For example, a four-module 7RU
chassis acts like a four-way N+1 array.
N+1 array indexing also accounts this type of functioning. Each 7RU chassis occupies a seg-
ment of N+1 addressing equal to the number of modules; i.e., 4 modules = 4 addresses.
The remaining N+1 functions remain the same. When one of the internal modules develops a
failure, it will be forced to mute by the internal SSPA controller. The unit will develop a sum-
mary alarm, but will remain in N+1 master mode (if it was prior to failure). Multi-module units
will delegate a new master mode only when all internal modules develop a failure.
Note : With multi-module RM SSPA chassis configurations, the N+1 system will
require fewer chassis to form a N+1 redundancy array.
Examples of 4-way N+1 systems:
One (1) four-module 5RU, 6RU, or 7RU chassis;
Two (2) two-module 5RU, 4RU or 3RU chassis;
Four (4) one-module 4RU or 3RU chassis.
3.8 N+1 Operational Basics (two or more units)
A system which utilizes two or more 7RU SSPA chassis in an N+1 configuration may be oper-
ated directly from the front panel as if it was a single very high power SSPA. Any 7RU SSPA
chassis in the system can serve as the Master Module single point of control.
3.8.1 Selecting the Master Module
The selection of the Master Module is fully automatic and shifts from one SSPA to another
based on the priority ranking assigned to the modules comprising each SSPA unit. A lower
priority index number (referred hereafter as the N+1 Address) means a higher rank in the N+1
hierarchy. The fault-free unit with the lowest N+1 address is selected as the N+1 Master Mod-
ule. The remainder of the units become N+1 Slave units.
Slave unit settings are under full control of the Master unit. Any system-related setting change
made on the Master Module automatically propagates to the Slave units to keep all units un-
der N+1 control in sync.
If the Master Module develops any kind of major fault condition, it delegates its Master privi-
leges to the unit which is next in N+1 ranking and becomes a slave unit. This type of control
architecture eliminates a single point of failure and achieves true N+1 system redundancy.
The Master Module is designated with a lit Online indicator and VFD display showing the
overall system state. See
Figure 3-10 .