Broadcast Centers spread the TEC's culture into adjacent systems and beyond. The spread of culture is represented by the phase lanes connecting systems turning their color. This increases allegiance at planets owned by you and your allies and decreases allegiance at enemy planets.
The TEC unlock the Broadcast Center after researching Interstellar Network. The TEC also have multiple upgrades that when used will improve the rate at which culture spreads as well as the debuffs to your enemy's empires should your culture invade their territory. Addictive Consumerism and Cultural Monopolization combined will increase culture spread rate by 20% and increases antimatter regeneration by 1.5. Critical Mass is an upgrade that once researched will reduce the amount of culture spread lost when it spreads through a planet. Foreign Sabotage is a powerful debuff that once in your enemy empires territory, will halt all ship production. One of the last upgrades is called Insurgency. This will periodically cause uprisings on your enemy empire's planets, causing militia troops to attack their territory.
The TEC rebels can research Liberated Resistance, which will periodically cause Insurgent forces to join your cause and rally at your empire's capital.