Just for reference, the description of C3 from Techmanual pg. 209
Introduced: 3050 (Draconis Combine)
The Command/Control/Communications (C3) system is easily
among the Inner Sphere’s most potent recent inventions. It is also
one of the most original, considering that it emerged not as the
result of a Star League tech recovery, but as a new application of
technologies. As much a revolution in battlefield technology as one
of combat philosophy for its creators in the Draconis Combine, the
system is essentially an elaborate tight-beam communications suite,
designed to link the sensors and targeting systems of up to a full lance
of friendly units in a single, closed network. The C3 system enables
those within its network to draw targeting data from one another and
coordinate fire with amazing ease. As long as effective weapon ranges
and lines of fire permit, a member of a C3 network can essentially strike
at a target with the same accuracy as the nearest friendly network
member. Moreover, units that mount a C3 master computer—with the
other network members using slave nodes—can use the computer’s
coordination as an improvised TAG system.
The system, of course, has its limits. Only units in the same network—
generally a single lance, though creative deployment of multiple
master computers per unit may allow for networks as large as a
company—may share targeting data in this fashion. Friendly units with
systems outside the network cannot simply “tap in” at will. Further, the
network signals and data streams are susceptible to jamming by enemy
ECMs. Worst of all, the hierarchical nature of the system means that the
loss of the master computer to destruction or ECM interference crashes
the entire network, leaving its surviving units to fend for themselves.
Sad to say, the biggest obstacle to optimum use of the C3 system is
a matter of ego more than technology. Ironically produced by a realm
with a strong sense of personal honor and a warrior’s code, the concept
of a communal targeting and communications network is often lost
on the warriors of the DCMS. Indeed, despite efforts to force a more
widespread distribution of the technology, this mentality has apparently
kept an otherwise powerful system virtually marginalized on the
battlefield, even as other factions adopt similar systems of their own.
And here's the rules from Total Warfare pg. 131
C3 COMPUTER (MASTER/SLAVE)
The C3 computer system can link up to twelve ’Mechs
or vehicles together—utilizing a series of C3 Master and
C3 Slaves—in a communications network that will share
targeting information.
To make an attack using a C3 computer network, calculate
the to-hit number using the range to the target from the
networked unit nearest the target with line of sight. Use the
firing unit’s modifiers for movement, terrain effects, minimum
range and so on. A weapon attack using a C3 network must
conform to standard LOS restrictions and cannot fire beyond
its maximum range, though a well-placed lancemate may
allow the firing unit to use his weapon’s short-range to-hit
number at long range.
The C3 network itself has no maximum range, but only units
actually on the playing area can benefit from the network, and
the C3 Master (or C3 Masters if using a company-sized network)
must be on the playing area.
TAG: The C3 Master (but not the C3 Slaves) exactly duplicates
the function of target acquisition gear (see TAG; p. 142).
LRM Indirect Fire: C3-equipped units spotting targets for
or launching an LRM indirect fire attack use the LRM Indirect
Fire rules (see p. 111), and gain no benefit from a C3 network.
Minimum Ranges: Minimum range is always determined
from the attacking unit to the target.
Variable Damage Weapons: The range, to determine
the Damage Value of a Variable Damage Weapon, is always
determined from the attacking unit to the target.
Stealth Armor: Armor that inflicts range modifiers against
attacking units does not confuse a C3 network. While such
additional range modifiers apply to the nearest attacking
unit, they do not apply to any other units using the network
to attack. However, some such systems (notably the Stealth
Armor System, p. 142) include their own ECM system; in this
case, an attacking unit must be outside the effective range of
the ECM mounted on the target unit, or the attacker gets cut
off from the network.
And this is from Techmanual pg.39 for how Mech sensors, sharing info, and targeting work in TT.
SENSORS AND TARGETING SYSTEMS
In its entirety, a BattleMech’s targeting and tracking (T&T)
system includes a sophisticated set of sensors and computers
to process data. These systems are getting ever more sophisticated
as technology is recovered and expanded…a fact that
might explain the Blakists’ recent interest in targeting electronics
manufacturers throughout the Inner Sphere.
Thermal imaging, light amplification, radar and magnetic
anomaly sensors are all among the primary sensors used by
BattleMechs, supplemented by seismic sensors, motion detectors,
chemical analyzers and a multitude of others. Despite
this broad range of sensor types, MechWarriors are not deluged
with raw data. Sophisticated computers streamline,
interpret and prioritize this information, so that by the time
the warrior gets the info, it appears as simple visual cues on
the usual cockpit displays or the warrior’s own neurohelmet
heads-up display (HUD).
The powers of a BattleMech’s sensory processors stand
out most strongly in their ability to recognize other units and
classify them by type and as friend or foe. Any T&T suite today
can inform a MechWarrior of the type of unit it detects, and
can even speculate on what variant it is, and the system is surprisingly
intuitive. Sometimes, this can present an interesting
effect, such as the famous example of the Inner Sphere naming
of the Clan Timber Wolf OmniMech. Upon an Inner Sphere
BattleMech’s first encounter with that ’Mech—which looked
like a cross between the familiar Marauder and Catapult designs,
the name “Mad Cat” was born. The ability to tell friend
from foe—another key ability of the T&T suite—eases the
burden of target identification for MechWarriors in the heat
of battle, particularly under poor visibility conditions.
BattleMechs are also not islands unto themselves. They can
share sensor data to some extent, allowing greater sensory
performance than a single ’Mech can achieve. The specialized
equipment of a C3 system takes this to new heights with direct
battlefield applications, but all BattleMechs can at least
receive basic sensory data from a unit mate.
And that data is recorded. BattleMechs have capable “black
box” systems, the so-called battleROM that stores hundreds
of hours of all sensor data from a ’Mech, from its internal and
external sensors and communications. The armored battleROM
recorder is located in the cockpit and will survive virtually
any catastrophe, from an ammo explosion to a failed
orbital drop.
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