Abstract: An improved circuit and method for connecting a device to an actuator-sensor interface (“ASI”) bus. The circuit provides the proper AC and DC coupling between the device and bus during normal operation, while providing AC and DC decoupling in the event of a short circuit or when the device is disconnected. The circuit accomplishes these goals while advantageously eliminating some of the components used in prior art circuits.

Abstract: An astable multivibrator with an R/C coupling network establishing a nominal operating frequency in the KHz range works into a chain of binary divider stages stepping down that frequency to the order of one Hz. The last stage output or outputs of the divider chain are connected to the coupling network through a feedback path including a switching transistor, driven into conduction during alternate half-cycles of the multivibrator, whereby the charging rate of the network capacitance is modified in slow steps with corresponding changes in operating frequency. Several intermediate stage outputs of the divider chain are tapped by way of a coincidence gate to energize a loudspeaker via an audio amplifier with a pulse train having a basic cadence of several hundred Hz, modulated by the feedback, and an on/off ratio well below 1:1.