Abstract: The Mini Packet Receiver Transmitter Circuit (MPRT) provides an interface between one or two eight bit microprocessors and a digital subscriber loop interface circuit. The bi-directional communication on a single wire pair is accomplished by alternating the subscriber loop receive and transmit frames controlled by a "Ping-Pong Protocol" using fixed frame format and bipolar alternate mark inversion (AMI) line encoding. There are two microprocessor ports within the MPRT, a transparent port for voice transmission and a non-transparent port for data trasmission. The MPRT implements the Mini Packet Protocol frame format as a mini packet (MP) of information, for both transparent and non-transparent data.

Abstract: The Asynchronous Packet Manager is the interface for transferring data in a first format between a data terminal equipment and a combination data and telephone switching system in a properietary packet format. A microprocessor accepts data from a universal asynchronous receiver transmitter and forwards the data to a mini packet receiver transmitter, when it is formatted into mini packets and converted to an alternate mark inversion signal and sent to the switching network.

Abstract: The Synchronous Packet Manager is the interface for switching synchronous data between a data terminal equipment and a combination data and telephone switching system in a proprietary packet format. A first microprocessor controlled circuit controls data to be received from the switching system or forwarded to it and communicates with a second microprocessor controlled circuit for controlling data to or from a terminal equipment via a common memory.

Abstract: An electronic circuit, for connecting a transmitter and receiver to a telephone line. The circuit operates on very low operating voltages from the line which allows parallel operation with a conventional set on long-loop applications. In its functional form, the circuit utilizes a bridge configuration having transistors in two of its legs, driven by the transmitter output, thereby eliminating the usual bridge balancing resistors therefrom and their concomitant operating voltage drops thereacross.

Abstract: In an electronic telephone a speech network for connecting a transmitter and receiver to a line powered telephone line which utilizes a bridge configuration that is so arranged that the network will function on very low d-c line voltages, thereby enabling the set to be connected in multi-party applications with a conventional hybrid transformer set on long loop applications.