Nortel Networks BCM50 manual Site telephony wiring requirements, Digital loop

76Chapter 6 Checking the installation prerequisites

Danger: Risk of electric shock

The safety of this product requires connection to an outlet with a third-wire ground. Use only with the supplied BCM50 power supply and a three-wire power outlet.

Caution: Check ground connections

Ensure that the electrical ground connections of the power utility, telephone lines, and internal metal water pipe system, if present, are connected together. If these ground connections are not connected together, contact the appropriate electrical inspection authority. Do not try to make the connections yourself.

You can connect the power supply to a power bar. The total length of the power cables from the power supply to the electrical outlet (including power bar) should not exceed 2 m (6.5 ft.). You must use a power bar approved by an appropriate National Test Body, with a third-wire ground. It is recommended not to use an extension cord between the power supply and the power bar, or between the power bar and the electrical outlet.

Site telephony wiring requirements

This section describes the requirements for wiring digital telephony devices (digital loop) and analog 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 77

Digital loop

The 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 taps

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