Abstract: A system for interconnecting a pair of communication systems comprising a pair of expansion switching matrices connected to bidirectional signal ports of the respective communication systems and interconnected via a plurality of signal paths, such as junctors. Control information is transmitted between central controllers of the pair of communication systems via a pair of serial data transmission circuits, such as universal asynchronous receiver/transmitters. Thus, predetermined ones of the signal ports of the separate communication systems may be interconnected via the expansion switching circuits independently of signal traffic within the respective communication systems. In addition, special features such as call ring back busy, may be implemented between signal ports of the respective communication systems as a result of control information being communicated via the serial data transmission circuits.

Abstract: A communication network advantageously uses existing broadcast channels to instruct remote receivers and eventually use automatic dial-up capability for forming a telephone communication link with a central processing facility. The network is capable of providing many services from remote reading of meters to electronic mail and electronic billing. The network is preferably shared by a number of large users communicating with a host of subscribers.

Abstract: A patient intercom arrangement for magnetic resonance imaging systems wherein the gradient noises are recorded and substracted from the voice plus noise signals received from the patient during scan procedures to provide clear and audible voice signals.

Abstract: A life safety system for monitoring a building has a plurality of detectors for detecting alarm conditions located throughout the building, a plurality of speakers located throughout the building, a source of pre-stored voice messages which can be broadcast over the speakers, and a telephone network. The improvement is a voice synthesizer for providing the source of pre-stored voice messages and a constant volume telephone system. The constant volume telephone system has a telephone line and a plurality of telephones which can be connected to the telephone line, and a power supply having an adjustable output voltage which provides the voltage for the telephone line. A sensing and adjusting circuit senses the number of telephones off-hook and causes the power supply to be adjusted in response to the number of telephones off-hook.

Abstract: An apparatus is disclosed for identifying who is placing a call to a telephone prior to answering. The apparatus, which is preferably located at the telephone central office, includes a switching matrix having a plurality of DID access lines coupling the switching matrix to the central telephone office. The switching matrix also has a plurality of input and output lines which are assigned to individual subscribers' telephones who desire to identify callers prior to answering. In the preferred embodiment of the invention, twenty DID access lines are used to couple the telephone central office to the switching matrix and one hundred subscription and input and output lines are used to couple the switching matrix to individual subscriber telephones. The switching matrix is coupled to a programmed microprocessor which controls the operation of the system including the generation of a digitally synthesized vocal announcement of at least the number being called.