The report describes the conversion of a 5 gm. teleradium unit to a 10 gm. unit. A detailed description is given of the measurement of the output, and the determination of dosage distribution in a water phantom. The dosage distribution was measured with a new “teledosefinder” system which enables the operators to work at a safe distance from the unit. Protection measurements on the radiation in the neighbourhood of the unit were made, and the protection was found to be satisfactory.