Abstract: A telephone handset interface is inserted between the telephone handset and base for automatic switching between voice and data modes of communication. Each station includes a telephone set with a base and handset, interface circuitry, and modem. The interface circuitry includes relay switches to couple the modem to the telephone base microphone and speaker lines in data mode and to couple the telephone handset to the telephone base in voice mode. The relay switches are controlled by a sensor that monitors the on-hook/off-hook status of the modem as an indication of when the modem is preparing to transmit or receive data. The interface circuitry also includes differential amplifier circuitry coupled to the telephone base speaker lines that enables the modem to continually monitor the telephone base speaker lines. In one embodiment, each modem includes circuitry for generating a start signal to cause a remote station at the other end of the communication link to enter data mode prior to transmitting data.

Abstract: A telephone interface system is inserted between the telephone handset and base to provide automatic switching between voice and data modes of communication. The interface includes a modem having a receive port coupled to the telephone base speaker lines and a transmit port switchably coupled to the base microphone lines, a switch for selectively coupling the telephone handset to the base, and a processor for monitoring data received by the modem and controlling the switch to automatically decouple the telephone handset from the base when data is being received or transmitted by the modem. The modem includes a tone generator that generates a predetermined start signal to signal a remote unit at the other end of the communication link to enter data mode prior to transmission of data. Similarly, the modem includes a tone detector to detect a start signal sent by the remote unit that causes the unit to switch into data mode in preparation for receiving data.

Abstract: A field monitoring device (FMD) for use in an electronic house arrest monitoring (EHAM) system has an infrared (IR) communications port concealed in the back of its housing. A strain relief fixture for the power cord covers the IR port during normal FMD operation. This strain relief fixture is removable only with a special tool. The IR port includes two small holes. Inside one hole is an infrared receiver. Inside the other hole is an infrared transmitter. Data communications with the FMD is established by optically linking a matching infrared receiver included in a coupling head of an IR adapter with the infrared transmitter within the FMD; and by similarly optically linking a matching infrared transmitter with the infrared receiver within the FMD. The IR adapter interfaces with a conventional data terminal, such as a personal computer, which data terminal functions as an external programmer for the FMD.