AT&T System 85 manual Phantom or Auxiliary Power, Terminating Resistors

ISDN 8503T Voice Terminal

Distance Limitations

For DEFINITY G2 and G3, in which multipoint configuration is used, the maximum signaling dis- tance possible from the port board to the work location jack is: (The terminating resistor should be within 250 feet of the work location; the distances listed are applicable for up to two voice ter- minals.)

If 24 AWG cable is used = 1600 feet

If 26 AWG cable is used = 1330 feet

Power Requirements

Phantom or Auxiliary Power

The 8503T voice terminal can receive power from the switch or from an auxiliary power supply. The installer can select the type of power used by setting two jumpers on the bottom of the voice terminal under a sliding plate between the Line jack and the Adjunct jack. A pictorial representa- tion of the jumpers is located to the right of the sliding plate. These jumpers are labeled PHAN (phantom power) and AUX (auxiliary power). The voice terminal is shipped in the PHAN position. You must verify that the jumper settings are set correctly for your configuration.

Note: The power jumpers must be set only by qualified service personnel.

PHAN (phantom power) should be selected when power is provided by the PBX. When the jumpers are set to PHAN, less than one Watt of power will be drawn from the switch to support normal operation.

AUX (auxiliary power) should be selected when power is provided in the closet. When the jumpers are set to AUX, the 8503T voice terminal will operate on a nominal 40 or 48 Vdc, UL-listed Communications Circuit Power source.

Terminating Resistors

The terminating resistor jumpers are located on the bottom of the voice terminal under a sliding plate between the Line jack and Adjunct jack. These jumpers enable (ON) or bypass (OFF) the terminating resistor. The set is shipped with the jumpers in the OFF position bypassing the ter- minating resistor. You must verify that the jumper settings are set correctly for your configura- tion.

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