On the other side of the signal fence lay the heavily guarded "protective strip" (Schutzstreifen), 500 to 1,000 metres (1,600 to 3,300 ft) wide, which adjoined the border itself.[1] It was monitored by guards stationed in concrete, steel and wooden watchtowers constructed at regular intervals along the entire length of the border. Nearly 700 such watchtowers had been built by 1989;[2] each of the larger ones was equipped with a powerful 1,000-watt rotating searchlight (Suchscheinwerfer) and firing ports to enable the guards to open fire without having to go outside.[60] Their entrances were always positioned facing towards the East German side, so that observers in the West could not see guards going in or out.