Abstract: In a private branch exchange apparatus having a plurality of extension ports, each extension port capable of connecting a push button telephone and a general standard type telephone in parallel, when a call occurs at one extension port where the parallel connection has been done, a ring sound can be produced at the push button or standard type telephone selectively. An additional dialling provides the selection between the push button and the standard type telephone. A memory may specify either of the push button or standard type telephone to be ringed. A call between the push button telephone and the standard type telephone can be provided in accordance with the additional dialing or data stored in a memory.