Abstract: Apparatus and method for testing the connection (i.e. solder joint) between an input/output (I/O) pin of an integrated circuit and a conductive trace of a printed circuit board (PCB). The internal circuitry of the integrated circuit is isolated from each I/O pin, and a first voltage source is coupled to each I/O pin via a respective pull-up load resistor. A tester circuit is coupled to each conductive trace of the PCB and compares the voltage V.sub.T thereon with a high threshold level (HTVL) and a low threshold level (LTVL) to test for a proper connection. Voltage V.sub.T is derived for an I/O pin under test when a resistive element, which is part of the tester circuit, is operatively coupled between the corresponding conductive trace and a second voltage source. If V.sub.T is below the LTVL or above the HTVL, the I/O pin is improperly coupled to the conductive trace. If V.sub.T is between the LTVL and HTVL, then the voltage on each of the other traces is compared to the HTVL.

Abstract: A decoupling capacitor and protection circuit is provided that will assist the power supply network in stabilizing the voltage near circuits that demand short rapid transitions in electrical current. The protection circuit also significantly reduces the amount of electrical current drawn by defective large area decoupling capacitors. An inverter stage controls a switching circuit connected in series with a decoupling capacitor. A feedback circuit is provided from the output of the capacitor to the switching circuit. If the capacitor goes bad, then a voltage is present on the feedback circuit and the switching circuit ensures that the output of the failed capacitor is presented with an open circuit so that the short circuit current flow through the capacitor is eliminated. In this manner, the integrity of the other circuits located near the failed capacitor will operate appropriately.

Abstract: A mechanism for automatically enabling and disabling clock signals includes a driver for providing a clock signal as an output, a gate coupled to the driver, and a sensing circuit coupled to both the output of the driver and to the gate. The sensing circuit provides a signal to the gate responsive to the output being in a first state. The gate then prevents the driver from driving the clock signal responsive to the signal from the sensing circuit. In one embodiment, a generator is coupled to the driver for providing a waveform to the driver. The driver then provides the clock signal based on this input waveform. Additionally, the gate is situated between the generator and the driver. The gate, based on the output of the sensing circuit, can then prevent the waveform from being provided to the driver.

Abstract: In a circuit arrangement for coupling a first signal into a second electric signal formed as an alternating signal, a device is provided for compensating for effects of the coupling on the signal pattern of the second signal, particularly on the "pulse tilt" of the second signal. In a preferred variant of the circuit arrangement, the coupling is inductive, whereby the compensation device comprises a capacitively functioning element. The circuit arrangement is particularly suited for coupling a direct-voltage signal into an alternating-signal bus.

Abstract: A signal isolation apparatus has a first transformer with a primary winding tap receiving an input signal and another primary winding tap receiving a first oscillating signal. A second transformer has a primary winding tap receiving the input signal and another primary winding tap receiving a second oscillating signal. The second oscillating signal is out of phase (typically 180 degrees out of phase) with the first oscillating signal. A rectifier electrically connected between a first secondary winding tap of the first transformer and a first secondary winding tap of the second transformer has a high output terminal and a low output terminal, the low output terminal being referenced to a second secondary winding of the first and second transformers. A signal across the high and low output terminals is an output signal galvanically isolated from the input signal with the same electrical characteristics as the input signal.

Abstract: A transistorized source power coupler for coupling a power source to a pair of transmission lines. DC power from the power source is conducted by the transistorized source power coupler to the transmission lines. Meanwhile, AC signals on the transmission lines are isolated from the power source by the source power coupler. Consequently, the same pair of transmission lines can be used to supply power to cells of a communications system while also conducting data signals between those cells with minimal effect to the power source.

Abstract: A quick recovery AC coupling circuit has a coupling capacitor stage that generates an output DC-biased AC signal by capacitively coupling an input DC-biased AC signal generated by a source stage. The output DC-biased AC signal is biased by a biasing stage. The quick recovery AC coupling circuit utilizes an emitter follower which is biased at its emitter by an active device in both the source stage and the biasing stage to maintain the bias voltage across the coupling capacitor stage when the quick recovery AC coupling circuit is powered off and when a high-input impedance device is connected to receive the output DC-biased AC signal.