PROBE FOR POSITION DETERMINATION

摘要

The batteries of a probe (10) are replaced by a dummy battery (30) which is connected to a an external controller (44,45) by wires (32,134) leading from the dummy battery terminals (36,38). The external controller (44.45) supplies a constant voltage to the probe (10) and also sends messages to the probe consisting of pulses of higher voltage. A comparator circuit within the probe compares the voltage at the dummy battery terminals with a known reference and sets a logic level high or low, thus enabling a serial data stream to be communicated to a programmable device within the probe. The probe may respond by sending a message back to the external controller, for example by modulating the current drawn through the battery terminals, sending an optical signal or by other means.