Abstract: A method for the systematic and efficient synthetic preparation and identification of metabolites of a pharmaceutical product in order to study possible toxic and/or otherwise biologically-active metabolites of such pharmaceutical products as early and conveniently as possible in the very expensive drug development process, comprising adding samples of the pharmaceutical product to a series of combinations of a synthetic metalloporphyrin (SMP) with a synthetic metalloporphyrin-co-oxidizing reagent in the presence of a suitable solvent, under specified conditions, in a manner such that each sample of pharmaceutical product is reacted with a different combination of synthetic metalloporphyrin, SMP-co-oxidizing reagent and solvent, followed by separation and isolation of the resulting oxidative products, then confirmation of the identity of metabolites from the pre-identified oxidative products by appropriate animal model studies, and subjecting the actual metabolites prepared in larger quantities by the above m

Abstract: An office line interface circuit includes a DC circuit for extracting a DC signal component from the office line current, an AC circuit for extracting an AC signal component from the office line current to supply the extracted AC signal component to the receiver of a telephone set, an impedance circuit switchably connected to the office line, and a switching circuit for connecting the impedance circuit to the office line when the extracted DC signal component exceeds a predetermined level to maintain at a substantially constant value the impedance of the office line as viewed from the telephone set. With this interface circuit, the sidetone preventing circuit for the telephone system can operate satisfactorily without complicating the construction under any office line condition.