Lo-Vs were arranged in mixed trains consisting of trailer cars and motor cars. While trailer cars were equipped with brakes, but no air compressors or motors, motor cars were equipped with all three. "Lo-V" is short for "Low Voltage" which refers to the cars' form of propulsion control. Earlier Composite and "Hi-V" (High Voltage) equipment that ran on the IRT had utilized a 600 volt DC circuit that ran directly through the motorman's master controller to control the car's propulsion. The 600 volts was also trainlined through the whole train by the use of high voltage jumper cables which had to be run between cars. However, Lo-V equipment used battery voltage (32 volts) in the motor control circuit to move high voltage (600 volt) contacts underneath the car, which would control the car's propulsion. Likewise, it would no longer be necessary to use 600 volt jumpers between the cars. This tremendously improved safety of the equipment for both train crews and shop personnel alike.
Standard Lo-V cars also simplified braking for train crews. On IRT equipment, an electric brake could be utilized to synchronize a braking effort and apply each car's brakes simultaneously and uniformly throughout the train. This was different from operating strictly using air (pneumatically), which was less responsive, but would still stop the train albeit more slowly. Lo-V cars simplified the braking process. On earlier IRT equipment, the braking notches were different for a motorman depending on whether or not he was operating electrically or pneumatically. On Lo-V cars, the notches were identical regardless of whether or not the electric brake was active. The braking system on a Lo-V car is known as AMUE.