The Commonwealth Pacific Cable System (COMPAC) was an undersea telephone cable system linking Canada, Hawaii, Fiji, New Zealand and Australia. At a cost of $100 million, the link contained 11,000 miles of telephone cable, which provided 80 two-way speech channels or 1,760 teleprinter circuits. The Overseas Telecommunications room still exists under Queen Elizabeth Drive between 2nd and 3rd ramps. It was originally staffed by people who would relay information using morse code.

The cable has existed in different forms for over 100 years and it has been upgraded a number of times. The room was known as the Cable House and was originally operated by the Australasia and China Telegraph Company. In 1911 the cable room was under a band rotunda in the park at Sth Bondi. Every now and then the cable is exposed when the beach is eroded by big seas.