Abstract: A system for IP telephony that utilizes distributed gateways instead of centralized gateways for communication between IP Telephones on a Packet Based Digital Network (PBDN) and Telephones on a Public Switched Telephone Network (PSTN). The system is based on the use of IP Telephone apparatuses (“Gateway Telephones”) wherein each is connected both to the PBDN and a PSTN and includes a built-in gateway between the two network connections. The gateway capacity of the system thus increases automatically with the number of Gateway Telephones. Gateway Location Servers facilitate the selection of a Gateway Telephone to serve as a gateway for a specific telephone call.

Abstract: A PCMCIA smart card reader with no protruding portion, with a stable mechanical design, allowing space for additional functions to be included in the PCMCIA card and that eases the insertion of a smart card. A thin support is formed between a thin upper section and a lower section of the PCMCIA smart card reader at an opening forming a smart card slot. The support is outside the smart card slot, but positioned within the PCMCIA slot and is preferably an integrated part of a PCMCIA card top cover. Since the support guides the smart card laterally at the opening of the smart card slot, only a small portion of the smart card has to be inserted into the PCMCIA card. The limited insertion of the smart card and the location, of contacts for interfacing with the smart card in the thin upper section of the smart card reader, creates space for other functions to be included in the PCMCIA card, for example, a modem. The smart card insertion is eased by a removable extension supporting.

Abstract: A detector for On-Hook/Off-Hook state of a telephone line includes a capacitor connected to the telephone line in series with a resistance large enough to be allowed as load on an On-Hook telephone line. A low impedance voltage sensing means in series with a normally open switch is connected across the capacitor, and the switch is closed in response to a polling signal to determine if the line is in On-Hook state. The capacitor transforms a very low charging current lasting seconds into a large discharge current lasting only milliseconds. This makes it possible to use an inexpensive low impedance voltage sensing device, such as an opto-coupler in series with a zener diode. Such components provide high-voltage galvanic insulation at low cost, and a very compact apparatus can be made. The invention also provides for inexpensive ring detector circuits and for overload protection for the equipment connected to the telephone line.

Abstract: A line state detector for a telephone line tests a voltage derived from the telephone line by closing a switch in series with a voltage sensing circuit in response to a polling signal. A modem testing the line state go Off-Hook immediately after it finds that the line was in On-Hook state, so it can use a low impedance voltage sensor directly on the telephone line. Monitoring equipment will need a line state detector with high impedance, which can be achieved by a high impedance in series with a capacitor. The capacitor voltage can then be tested by a low impedance sensing circuit.