VOICE OVER IP CRASH COURSE - voiceip.com.ua

54Chapter 2Figure 2-12In the cablevault, the largecables shownon the left arebroken downinto the smallercables on theright fordistributionthroughout theoffice.The Central OfficeBy now our cable has traveled over aerial and underground facilities andhas arrived at the central office. It enters the building via a buried conduitthat feeds into the cable vault, the lowest sub-basement in the office.Because the cable vault is exposed to the underground conduit system, adanger always exists that noxious and potentially explosive gases(methane, mostly) could flow into the cable vault and be set afire by aspark. These rooms are therefore closely monitored by the electronicequivalent of the canary in a coal mine and will cause alarms to sound ifgas at dangerous levels is detected. A cable vault is shown in Figure 2-13.Figure 2-13Another viewof the cablevault