Abstract: A power amplifier includes negative and positive terminals for connection across a direct current supply, an input for receiving a reference signal and an output for supplying an amplified replica of the reference signal. Positive polarity and negative polarity energy transfer gates are controlled to store electrical energy from the direct current supply, and to subsequently release electrical energy to the output. A control circuit is responsive to the reference signal and a potential amplitude at the output, for controlling which of either or neither of the positive polarity and negative polarity energy gates is active, and for controlling each quantity of electrical energy stored by an active one of the energy gates so that the amplified replica of the reference signal is provided. In an example, the power amplifier is used to efficiently generate ringing battery signals for use in a telephone facility.

Abstract: A multi-subscriber warning system can, in instances where emergencies are impending, apply ringing current to the "ring" lines of one party systems, to the "ring" lines of "ring" two party systems, and to the "tip" lines of "tip" two party systems. Those ringing signals will actuate the "ringers" of all instruments which are not in use, and will cause a buzzing sound in the reproducers of all instruments which are in use. Further, if a subscriber hears the "ringers" and raises the receiver from the cradle, a buzzing sound will be heard; and then the ringing sound will resume when the receiver is placed on the cradle. Conversely, if a buzzing sound is heard by a subscriber using the instrument, a ringing sound will be heard when the instrument is placed on the cradle; and the buzzing sound will resume when the receiver is again removed from the cradle. The duration and number of ringing sounds can be varied; and preferably will be different from the normal ringing sounds used to "call" a subscriber.

Abstract: A ring generator capable of supplying a plurality of predeterminedly selected distinct voltages each having a predetermined high amplitude and a predetermined frequency to a telephone line comprises a programmable computer having a low amplitude version of the plurality of voltages stored therein in digital form, the computer being responsive to predetermined control signals to select a desired one of the low amplitude version of the plurality of voltages stored therein, a first circuit arrangement coupled to the computer to convert the select one of the low amplitude version of the plurality of voltages to an analog version thereof and to increase the analog version to the predetermined high amplitude prior to coupling to the telephone line and a second circuit arrangement coupled to the first circuit arrangement, the telephone line and the computer to monitor the selected one of the plurality of voltage coupled from the first circuit to the telephone line to detect the operating condition of the ring genera