An integrated circuit card, such as PC Card, is provided in which a step-down converter in the form of a switching regulator provides a stable operating voltage at increased current beyond what is normally available from a single source. In particular, a quiet and stable power supply is obtained by modifying the standard configuration of a switching regulator such that the catch diode, or free-wheeling diode, instead of being connected to ground at the non-blocking terminal, is connected to a primary voltage source approximating the desired output voltage. If the desired output voltage is 5V, for example, the catch diode may be connected to Vcc supplied by a PC Card slot, which nominally supplies 5V. The block terminal of the catch diode is connected through the switch of the switching regulator to a higher, supplementary, voltage source, e.g. Vpp=12V in the case of a PC Card slot. During operation of the integrated circuit card at lower power levels, the primary voltage source is able to supply substantially all of the required power, such that the switch of the switching regulator may remain predominantly open, minimizing switching noise. During operation of the integrated circuit card at higher power levels, the switching regulator boosts the output voltage just enough to compensate for voltage droop. The integrated circuit card is therefore supplied with a stable, low-noise source of power.

A communication system for communicating between a first device and a second device is disclosed. The first device includes a first processor and a first memory, while the second device includes a second processor a second memory. The processors allow communication between the devices when an identical identification code is stored in both devices. In response to a user command, the first processor replaces an old identification code with a new identification code in a first memory location of the first memory. In response to a request signal from the first device, the second processor replaces the old identification code in a first location of the second memory with the new identification code. In response to an acknowledge signal from the second device, and after verifying that the new identification code is included in the acknowledge signal, the first processor replaces the old identification code in a second memory location of the first memory. Further, the second processor replaces the old identification code in a second location of the second memory with the new identification code after verifying that the new identification code is included in another acknowledge signal from the first device.

A mobile communication terminal includes an IC card, a power supply, and a control section. The IC card stores an identification number. The power supply supplies power to the mobile communication terminal. The control section can set the mobile communication terminal to a communication possible state when the power is supplied from the power supply and an entered identification number is coincident with the identification number stored in the IC card. Also, the control section can set the mobile communication terminal to the communication possible state depending on a power down time period without an entering operation of the identification number when the supply of the power to the mobile communication terminal is stopped and then recovered.

A system for supplying primary electrical power to modular components of electronic equipment. The system uses a battery power source mounted either in the module or as part of a battery pack that attaches to the module. Module circuitry supplies a recharge current to the battery power source. A charge circuit charges the batteries in a parallel and supplies power to the module by connecting the batteries in series. Circuitry also determines the amount of battery power source used for an operation of the module and sends a recharge current to the battery power source corresponding to the power consumed by the module and based on the available recharge current.

An object of the present invention is to provide a portable terminal suitable for a videophone using a multicall and a portable wireless equipment which communicate voice and data at the same time, and which is small and thin and has excellent portability, without being affected by a human body, at the time of conversation. Therefore, a radio unit which requires large power for the communication with the base station and hence is difficult to be made small and a user interface unit which is actually operated by a user are separated, and connected by radio communication with small power.