Indirect TPMS, or Indirect Tire Pressure Monitoring System, is a technology used in vehicles to monitor tire pressure without using dedicated sensors in each tire. Instead, it relies on the vehicle's existing wheel speed sensors, which are part of the anti-lock braking system (ABS). By comparing the rotational speed of each tire, the system can detect differences that indicate a loss of pressure in one or more tires. When a tire loses pressure, it typically has a smaller diameter and rotates faster than properly inflated tires. The indirect TPMS alerts the driver through a warning light on the dashboard, prompting them to check the affected tire. This system is often less expensive to implement than direct TPMS, which uses individual sensors in each tire.