 There are 55 medic units spread across the stations, including 42 advanced life support (ALS) and 18 basic life support (BLS) units.For special events, or to meet staffing requirements, the advanced life support (ALS) medic units may be downgraded to basic life support (BLS) units.A BLS unit will contain a 'B' in their call sign, for example "Medic 9B".