A medical instrument, comprising: a shaft for insertion into a body of a patient; one or more position sensors fitted at a distal end of the shaft; a connector, configured to removably receive a mating connector; interrogation circuitry, which is configured to detect whether the mating connector is connected to the connector, and, if not connected, to prevent tracking a position of the distal end in the body using the one or more position sensors; and enablement circuitry configured to validate position-tracking terms-of-use, and to enable tracking the position of the distal end only when the terms-of-use are valid, wherein: the enablement circuitry comprises a Radio-Frequency Identification (RFID) circuit that is configured to validate the position-tracking terms-of-use, and to enable tracking the position of the distal end only when the terms-of-use are valid; or the terms-of-use include a preset maximal number of usage sessions not having been reached, the mating connector further comprising a counter circuit, which is encoded with the preset maximal number of usage-sessions of the medical instrument and is configured to indicate to the enablement circuitry whether the preset maximal number of usage-sessions has been reached, wherein the enablement circuitry is configured to prevent tracking the position of the distal end, upon receiving from the counter circuit an indication that a preset maximal number of usage-sessions value has been reached. a shaft for insertion into a body of a patient; one or more position sensors fitted at a distal end of the shaft; a connector, configured to removably receive a mating connector; interrogation circuitry, which is configured to detect whether the mating connector is connected to the connector, and, if not connected, to prevent tracking a position of the distal end in the body using the one or more position sensors; and enablement circuitry configured to validate position-tracking terms-of-use, and to enable tracking the position of the distal end only when the terms-of-use are valid, wherein: the enablement circuitry comprises a Radio-Frequency Identification (RFID) circuit that is configured to validate the position-tracking terms-of-use, and to enable tracking the position of the distal end only when the terms-of-use are valid; or the terms-of-use include a preset maximal number of usage sessions not having been reached, the mating connector further comprising a counter circuit, which is encoded with the preset maximal number of usage-sessions of the medical instrument and is configured to indicate to the enablement circuitry whether the preset maximal number of usage-sessions has been reached, wherein the enablement circuitry is configured to prevent tracking the position of the distal end, upon receiving from the counter circuit an indication that a preset maximal number of usage-sessions value has been reached. the enablement circuitry comprises a Radio-Frequency Identification (RFID) circuit that is configured to validate the position-tracking terms-of-use, and to enable tracking the position of the distal end only when the terms-of-use are valid; or the terms-of-use include a preset maximal number of usage sessions not having been reached, the mating connector further comprising a counter circuit, which is encoded with the preset maximal number of usage-sessions of the medical instrument and is configured to indicate to the enablement circuitry whether the preset maximal number of usage-sessions has been reached, wherein the enablement circuitry is configured to prevent tracking the position of the distal end, upon receiving from the counter circuit an indication that a preset maximal number of usage-sessions value has been reached.