[en] It was decided in the summer of 1977 to replace and upgrade part of the electronics of the OSTR console. The console was the original system installed in 1967 when the reactor first went critical. Although it was generally quite reliable, maintenance was becoming more frequent, and locating spare and replacement parts was getting very difficult. The upgrading would replace the majority of the system with new, state- of-the-art electronics. The new, upgrading package consisted of replacing the left-hand console electronics drawer; specifically: 1. The present multirange linear channel using an ion chamber was replaced by a new 9.5-decade linear channel driven by a fission chamber. No scram features are on the new linear channel. 2. The present multirange log channel with a period circuit using an ion chamber was replaced by a new 10-decade wide- range log channel, also with a period circuit, driven by a fission chamber. The same fission chamber drives the new linear and wide-range log channels. 3. The present count-rate (startup) channel using a fission chamber was removed. Its function was taken over by the new wide-range log and linear channels. 4. A new safety channel with scram capability, driven by an ion chamber, was added. 5. A new fuel element temperature circuit with scram capability was added. The upgrading package was ordered in February 1978 and installation was completed in January 1980. One of the biggest time delays in the process was the NRC review time of the Technical Specifications amendment that was requested for this change. The actual installation of the new package required five weeks, including functional testing. The linearity of the new instrument systems is excellent, and the wide-range capability of the new log and linear channels provides increased operational flexibility and accuracy, especially when a low power run immediately follows a high power run. (author)