In one embodiment, a first device includes an electrically conductive element that is configured to capacitively couple to an electrode of a second device emitting a first electrical signal. The electrically conductive element is further configured to communicate to a circuit of the first device a second electrical signal induced in the electrically conductive element by the first electrical signal and through the capacitive coupling. The circuit of the first device is coupled to the electrically conductive element and is configured to receive the second electrical signal. The circuit is further configured to produce an electrical response to the second electrical signal, where the electrical response of the circuit is based at least in part on one or more characteristics of the first electrical signal.