US Patent 7738917 Intercom/wireless door bell for multi-handset telephone system

A multi handset telephone system with a wireless telecom/doorbell module. The telecom/doorbell module has similar electronics as a cordless handset that includes audio and RF link with a base unit. A speakerphone functionality of a wireless telecom/doorbell audio processor is used to provide an intercom audio conversation. The wireless intercom/doorbell module is battery powered that is either charged by an AC adapter or by an existing doorbell wiring. The wireless intercom/doorbell module also work in parallel with the existing bell wiring. When a page key is pressed, the module pages the telephone system and shorts the doorbell wiring to make an existing bell ring. The doorbell module is coupled with a camera.