HID headlamp bulbs do not run on low-voltage DC current, so they require a ballast with either an internal or external ignitor. The ignitor is integrated into the bulb in D1 and D3 systems, and is either a separate unit or part of the ballast in D2 and D4 systems. The ballast controls the current to the bulb.
In the larger Montreal Census Metropolitan Area, 67.9% of the population speaks French at home, compared to 16.5% who speak English. Montreal is one of the most bilingual cities in Quebec and Canada with 56% of the population able to speak both English and French. Montreal is the second largest primarily French-speaking city in the world, after Paris. Montreal was named a UNESCO City of Design.
In 2011 the city had a population of 1,649,519. Montreal's metropolitan area had a population of 3,824,221 and a population of 1,886,481 in the urban agglomeration, with all of the municipalities on the Island of Montreal included. The 2014 estimate of the population of the metropolitan area of Montreal is 4.1 million. French is the city's official language and is the language spoken at home by 56.9% of the population of the city, followed by English at 18.6% and 19.8% other languages (in the 2006 census).