PBX telephone exchange with reduced number of cross points - uses through connection matrix with cross points coacting in enquiry calls

摘要

The number of crosspoints involved in an enquiry call is kept as small as possible. This is achieved by operating the through connection coupling matrix as a reflection matrix, when in its through connection mode, and by connecting its second connecting level to a through connection enquiry coupling network whose other connection level is connected to the enquiry outputs of the line transformers. For constructing enquiry connections both the two line transfer circuits and the through connection coupling matrix are involved.