Abstract: A probe tip is employed to measure electromagnetic fields without the use of a metallic conducting wire or cable which would otherwise distort the field being measured. The probe tip includes a variety of different circuits, each of which contains a separate battery, a powered field measurement sensor and an amplifier. A light source, which is internal to the probe tip and coupled to the amplifier, operates to convert the measured field to an analog optical signal. The analog optical signal is transmitted via an optical fiber to a receiver/preamplifier circuit which converts the optical signal to an electrical signal at the fiber's far end. This receiver/preamplifier device can be coupled directly to an oscilloscope or other instrument which are employed and used for the display or recording the magnitude of the electromagnetic field as measured by the probe.

Abstract: A level comparator is used to check the incoming message header pulse amplitude and if it is of a level higher than an established level a signal is transmitted to update a digital counter whose digital output is converted by a digital to analog converter to establish an increased analog reference level. If the incoming message header is lower the counter is decremented to establish a lower reference level. Then the levels of any signals present at fixed intervals after the header or sync pulse are measured and recorded. These measured levels constitute the value of correction required for subsequent pulses and are added to or subtracted from following data pulses as required.

Abstract: A circuit arranged to measure and correct for transmission line induced disturbances at discrete intervals after receipt of a header pulse by recording the presence of any voltage deviating from a set level. These levels are registered and during receipt of the data pulses are utilized at times corresponding to the relative position of the preceding data pulses to modify subsequent data bits.

Abstract: A power converter which supplies AC or positive or negative DC output voltage with positive or negative current while isolating the output voltage from the input power source. This converter includes a pulse width modulator converts power amplitude signals to pulses of proportionate width. A power driver circuit applies these pulses to a sychronous demodulator and low pass filter via a pulse transformer. A low output impedance is presented to all output disturbances such that the converter can source or sink current in true four quadrant operation, including the passing of power from output to input when a load voltage exceeds the intended supply voltage.

Abstract: A microcomputer controlled key telephone line circuit for use in a key telephone. A microcomputer is used to sequentially and alternately scan the ringing leads and tip and ring leads associated with connected line circuits and A leads associated with connected telephone stations. The microcomputer operates in response to changes in the status of these leads to control the normal key telephone functions such as line pickup, hold and ringing current detection, lamp illumination and tone signaling.