Electrical current and/or conductivity in an electrical current channel varies in response to spatiotemporal magnetic flux pattern and/or to variation in electromotive force (EMF). For example, a channel with time-varying electrical conductivity can have induced electrical current variation due to flux pattern resulting from electrical current in another channel or set of channels; the current variation can increase magnetic flux density. The electrical currents can be transient electrical currents, and can cascade to amplify a resulting electromagnetic waveform. A channel can include the channel of a zener or zener-like diode or of a transistor, as well as an extended conductive channel. Channels can be configured in electrical current loops and in various orientations and combinations to obtain current and/or conductivity variation. A transient electrical current can be triggered in a channel, e.g. by an EMF peak, and circuitry with a combination of EMF triggering components can perform logical and timing operation.