Other new features of the upgrade, carried out by up to 200 engineers, include a clearer public address system with more than 300 speakers, and an improved customer information system. Wall tiles and lighting have been replaced and 19 new help points have been installed, all of which are managed from a new control room on site. Construction teams from Tube Lines - responsible for maintenance on the Jubilee, Northern and Piccadilly lines - carried out the whole upgrade between midnight and the first Tube train service each morning to minimise disruption.