This circuit is from a PopularElectronics of June 1992. The magazine no longer exists, but the circuit can be implemented with BC548 and BC558 transistors. The photo-receiver can be any Darlington and the phone must be crystal or piezoelectric. The transmitter for this receiver is the CIR1904. The circuit is powered by a 9 V battery and its consumption is very low. Optical resources must be used to achieve greater range.