Abstract: An information signal to be communicated to a roof-mounted light bar or other electrical or electronic device travels over the vehicle's or other environment's power bus or other power conductor. In one exemplary illustrative non-limiting implementation, a modulated current load draws power supply current in an amount that is instantaneously responsive to at least some characteristic of the information signal to be communicated. This modulated current loading induces the vehicular or other power supply (e.g., DC battery) to modulate its output voltage in a manner that is responsive to the modulated current loading. A voltage sensor and demodulator also connected to the power bus senses the resulting voltage fluctuations and demodulates those fluctuations to recover or regenerate the original information signal.