schaltungsanordnung for a small fernsprechnebenstellenanlage (heimtelefonanlage)

摘要

The telephone system for installation in a home allows one main and four extensions to make internal calls or use the exchange line. All telephones are normally switched to the house busbar. An internal call is made by lifting a receiver and dialling the called extension number. Other extensions can join in by lifting their receivers or can be called by dialling the numbers. The microprocessor switches the called extension to the exchange busbar and connects the ringing supply to it. When the called extension answers, the microprocessor switches it back to the house busbar. An incoming call on the exchange line is detected by the microprocessor, which switches the main to the exchange busbar and rings it. When the main answers, the exchange busbar is switched through to the exchange line. A loud bell can be switched on and an extension can answer an outside call by dialling the exchange code.