A method and apparatus to detect an off-hook state of a telephone connected in parallel to a communication terminal device connected to a telephone network. The magnetron is attached to a microwave transition and a lucent crucible. Then, the control signal is transmitted to a switch by the signal generator for controlling the switch to be turned on or turned off. Upon coupling of the male component with the female component, the check valve is caused to open through the interaction of a probe linked to the check valve which contacts a portion of the opposing coupler, thereby opening the check valve and permitting pressurized fluid flow between the two components. More particularly, the present invention relates to compounds represented by formula or their pharmacologically acceptable salts or solvates, or their diastereomer mixtures, antimicrobial agents comprising them, and a process for producing them.