With the charging circuit off, the receiver and telemetry equipments continue to draw constant power from the batteries. (Electrically, power = voltage x current). As the battery voltage gets lower, the current increase to the point of failure. In the case of the Ashtech receivers BSL engineers have found the on/off switch is a circuit breaker. The breaker trips at low voltage (high current) levels. After an extended power outage, the receiver appears to have been turned off. The low voltage cut-off device protects equipment, and eliminates the need to visit a station after an extended power outage. Low-voltage cut-off devices were installed at all new stations and stations at SAOB, YBHB, FARB, SUTB and CMBB were upgraded with the devices.