The cable is made of steel wires covered by an inner conductor, dielectric outer conductor and sheath. If the cable is laid in shallow sea, it is armored, in deep sea, this is not necessary. The cables have repeater amplifiers attached at intervals of several nautical miles to boost the strength of signals.
布放海纜除了電纜本身之外，還附帶兩種不可或缺的設備：一種是「中繼器」，也就是「放大器」，每隔數海浬在電纜上裝設一具，這是海纜系統的心臟，能使傳遞過程中漸趨微弱的訊號增強。