Fujitsu Corporation

Kazuyuki Minohara

Kenji Takato

Kazuhiro Yoshida

Isamu Fukuda

Kazumi Kinoshita

Nobuyuki Fukuda

Shigeaki Kawamata

Kiyoshi Kurosaki

Akihiro Kameda

Jun Roppongi

Taichi Kosako

Yoshinobu Imai

Takeshi Nishioka

A communication apparatus performs encryption on data transmitted from another communication apparatus by using first or second cryptographic algorithm, or performs decryption on the data that has been encrypted using the first or second cryptographic algorithm, by using one of the first and second cryptographic algorithms used for the encryption, where the second cryptographic algorithm provides a higher security level than the first cryptographic algorithm. The communication apparatus includes an encryption unit configured to perform, upon receiving the data including a cryptographic class identifying a parameter to be used for performing the encryption or the decryption, the encryption or the decryption by using one of the first and second cryptographic algorithms, based on the cryptographic class.

Apparatus and method for performing different cryptographic algorithms in a communication system

Ring trip deciding circuit

A two-wire termination impedance generation circuit of a subscriber circuit including differential amplifiers, which is provided with a network circuit including capacitors and resistors, an input point, and current sources, the capacitor being comprised of series connected first and second capacitors, the resistor being comprised of series connected first and second resistors and having a high band bypass capacitor connected at the intermediate connecting point of the same, and the resistor being comprised of a complex termination resistor forming an internal termination impedance and a series connected complex termination resistor and complex termination capacitor being connected directly to the telephone line as an external termination impedance, wherein the frequency characteristics can be improved in three ways.

Two-wire termination impedance generation circuit of subscriber circuit

A battery feed circuit supplies a feed current to a telephone set via a 2-wire telecommunication line formed of a TIP line and a RING line. The battery feed circuit includes a first voltage detection circuit for detecting a first voltage across the TIP line and a ground line, a second voltage detection circuit for detecting a second voltage across the RING line and a power line connected to a power supply of the battery feed circuit, a current source responsive to a first control signal for respectively generating first and second currents in the TIP and RING lines, the first and second currents being equal in magnitude and opposite in direction, the current source also varying the first and second currents in response to a second control signal so as to be in proportion to a common mode voltage across the TIP and RING lines, a first feedback circuit responsive to the first and second voltages detected by the first and second voltage detection circuits for generating the first control signal, and a second feedback circuit for generating the second control signal by detecting the common mode voltage across the TIP and RING lines.

Battery feed circuit for supplying feed current to telephone set

A ring trip detection circuit detects an OFF-hooked state of a telephone receiver during ringing of a telephone set by detecting a change in a voltage across two terminals of a transmission resistor through which a ringing signal is supplied to the telephone set from a ringing signal source. The ring trip detection circuit includes a voltage dividing circuit coupled to the two terminals of the transmission resistor for dividing voltages at the two terminals and for outputting divided voltages, a pair of transistors having bases for respectively receiving the divided voltages from the voltage dividing circuit, a constant current source, a pair of resistors having first terminals respectively coupled to emitters of the pair of transistors and second terminals coupled in common to the constant current source, where the pair of resistors have the same resistance, and a current mirror circuit coupled to collectors of the pair of transistors for outputting an output current which indicates whether or not the telephone receiver is OFF-hooked.

Ring trip detection circuit

Growing community of inventors

Yokohama, Japan

Kazuyuki Minohara