As built, the "Upholder" class was equipped with the Kelvin Hughes Type 1007 I-band radar for navigational purposes. The submarines were fitted with the Type 2040 Thompson Sintra ARGONAUTE hull mounted sonar, installed in the bow and Type 2026 GEC Avionics passive towed array. The submarines had the Type 2019 Thompson Sintra PARIS passive sonar for active and intercept purposes. They also had the Type 2041 passive ranging sonar and the Type 2004 expendable bathythermograph. The class was fitted with Type 2008 underwater telephone. The Type 2040 sonar was intended to be upgraded to Type 2075; however, that upgrade was cancelled in 1991.