76 Chapter 6 Checking the installation prerequisitesN0027152 01N0027152 01You can connect the power supply to a power bar. The total length of the power cables from thepower supply to the electrical outlet (including power bar) should not exceed 2 m (6.5 ft.). Youmust use a power bar approved by an appropriate National Test Body, with a third-wire ground. Itis recommended not to use an extension cord between the power supply and the power bar, orbetween the power bar and the electrical outlet.Site telephony wiring requirementsThis section describes the requirements for wiring digital telephony devices (digital loop) andanalog telephony devices (analog loop) to the BCM50 system.Refer to the following sections for information on the parameters for digital and analog loops:• “Digital loop”• “Analog loop” on page 77Digital loopThe following parameters must be met for a digital loop:• one, two, or three twisted-pair cables per telephone• dc loop resistance of less than 64 Ω• cable length (0.5 mm or 24 AWG) less than 300 m (975 ft.)• use of a station auxiliary power supply (SAPS) for loops 300 m (975 ft.) to 1200 m (3900 ft.).In North America, the SAPS must be a CSA- or UL-approved Class 2 power source.In Europe, the SAPS must be a Class II power source and CE marked.• no bridge tapsDanger: Risk of electric shockThe safety of this product requires connection to an outlet with a third-wire ground. Useonly with the supplied BCM50 power supply and a three-wire power outlet.Caution: Check ground connectionsEnsure that the electrical ground connections of the power utility, telephone lines, andinternal metal water pipe system, if present, are connected together. If these groundconnections are not connected together, contact the appropriate electrical inspectionauthority. Do not try to make the connections yourself.
