Brake controllers are used to control braking systems. They can simply engage and disengage the brake, or control the speed of engagement, breakaway torque, and other variables. Brake controllers receive inputs from sensors which monitor parameters such as position, speed, torque, lockup and slip status. Specifications for brake controllers include number of inputs, number of outputs, input types, and output types. The number of inputs equals the total number of signals sent to the brake controller. The number of outputs equals the total number of outputs used to control, compensate or correct the braking process. Input types for brake controllers include: direct current (DC) voltages, current loops, analog signals from resistors or potentiometers, frequency inputs, and switch or relay inputs. Output types include analog voltages, current loops, switch or relay outputs, and pulses or frequencies. Most brake controllers can also send inputs or receive outputs in serial, parallel, Ethernet or other digital formats which indicate a process variable. Some brake controllers can send and/or receive commands and inputs from information converted to an industrial fieldbus protocol.