Activation circuit for sealed electronic device

An electronic device comprising:

• sensor circuitry for gathering or sensing data;
• an internal battery for powering the sensor circuitry;
• an activation circuit for activating the sensor circuitry, the activation circuit including a receiver for receiving a radio frequency signal from an external source, a switch for connecting the battery to the sensor circuitry in response to the receiver, the switch being operable to maintain connection of the battery to the sensor circuitry after the radio frequency signal ceases, and a decoder for decoding the radio frequency signal and activating the switch only when a particular code is detected;
• and
• an environmentally sealed enclosure for housing the sensor circuitry, the internal battery, and the activation circuit, the enclosure having no external on/off switch or other components that could provide a pathway for water or other contaminants.

A data acquisition device comprising:

• sensor circuitry for gathering or sensing data, the sensor circuitry including a temperature sensor, a location sensor, a signal sensor, a sound sensor, or a motion sensor;
• an internal battery for powering the sensor circuitry;
• an activation circuit for activating the sensor circuitry, the activation circuit including—
• a receiver for receiving a radio frequency signal from an external source, the receiver including a band pass filter for passing only selected frequencies of the RF signal and attenuating frequencies outside the selected frequencies;
• a switch for connecting the battery to the sensor circuitry in response to the receiver, the switch being operable to maintain connection of the battery to the sensor circuitry after the radio frequency signal ceases, the switch comprising a transistor circuit including a transistor and a loopback connection between the transistor emitter and the transistor base;
• and
• a decoder for decoding the radio frequency signal and activating the switch only when a particular code is detected;
• and
• an environmentally sealed enclosure for housing the sensor circuitry, the internal battery, and the activation circuit, the enclosure having no external on/off switch or other components that could provide a pathway for water or other contaminants.