Abstract: A maintenance information providing server (Web server) 20 that transmits maintenance information to a portable terminal carried by a vendor or a customer is appended to the network management system (NMS) 21 supervising the network 2, server 20 on receipt of malfunction information from the NMS 21, notifying the malfunction to one or more pre-registered portable terminals (23, 13, 33) of a communication service purveyor, vendor or the customer.

Abstract: A maintenance information providing server (Web server) 20 that transmits maintenance information to a portable terminal carried by a vendor or a customer is appended to the network management system (NMS) 21 supervising the network 2, server 20 on receipt of malfunction information from the NMS 21, notifying the malfunction to one or more pre-registered portable terminals (23, 13, 33) of a communication service purveyor, vendor or the customer.

Abstract: The present invention provides an automatic identification level control circuit, an identification level control method, an automatic identification phase control circuit, an identification phase control method, and an optical receiver, capable of stably setting an optimal identification level or identification phase. An automatic identification level control circuit of the present invention includes a coupling capacitor, an identification circuit, a level fluctuation detection circuit, an identification voltage control circuit, and a low-pass filter. The identification circuit includes limiter amplifiers and flip flops. The level fluctuation detection circuit includes exclusive OR circuits.

Abstract: In an optical repeatered transmission system, an optical multiplex of a data signal and a supervisory signal is sent from a first terminal station. At an upstream repeater station, the optical signal is received and combined with excitation light energy supplied from a laser and amplified by an erbium-doped fiber with the excitation energy for transmission to a downstream repeater station. At the downstream repeater station, the optical signal is combined with excitation light energy supplied from a laser and amplified by an erbium-doped fiber with the excitation energy for transmission to a second terminal station. At the upstream repeater station, the supervisory signal is monitored. If it is determined to be lost, the excitation light energy of the station is modulated with a first fault-point indicating signal which is unique to the upstream repeater station and transmitted to the downstream repeater station instead of the optical multiplex signal.