Abstract: A dual mode transmitter/receiver adds two-way radio functionality to a frequency division duplex mobile phone. The dual mode transmitter/receiver allows short-range and low-power communication between similarly equipped phones. In the two-way radio mode, the dual mode mobile phone transmits and receives at a frequency between the normal mobile transmit and receive frequency bands so that a number of transmitter/receiver components are utilized for both normal and two-way radio communication.

Abstract: The disclosed optically coupled device includes one or more light emitting input semiconductor devices coupled by a transparent and electrically insulating medium to one or more output semiconductor devices which produce an electrical signal in response to the light received from the input device. Some such devices are known as opto-isolators or optically coupled isolators. In the disclosed devices the transparent medium is surrounded by a diffusely reflecting enclosure, which tends to make the device characteristics less sensitive to variations in fabrication. Efficient planar opto-isolator structures are disclosed.