A system comprising: a control device for altering conductance; and a partial power source comprising: a first material electrically coupled to the control device; and a second material electrically coupled to the control device and electrically isolated from the first material, wherein the first and second materials are selected to provide a voltage potential difference as a result of the materials being in contact with a conducting liquid, and wherein the control device alters the conductance between the first and second materials such that the magnitude of the current flow is varied to encode information in a signal radiated by the conducting liquid and the encoded information is remotely detectable by a receiver.