The different markets have specific requirements for how quickly batteries must be activated by an aggregator and the minimum levels of power that must be met. FFR is the fastest market, where the battery must be able to deliver full power within a few hundred milliseconds of receiving the signal. FCR-D, both up and down, allows a maximum reaction time of a few seconds. In both FFR and FCR-D, the battery needs to be active for a relatively short period. FCR-N does not require the same speed but demands longer endurance, typically around 1 hour.