Specifications

33
TELCO Ground Reference
3. Connect one end of the 50-pin SCSI cable to the SCSI drive with the stripped edge
toward the drive's power connector. Connect the other end to connector J1 on the
Pentium CPU card (see Figure 6). The stripped edge should be towards pin 1,
which means the bottom on the card.
4. Connect the power cable to the mating connector at the left end of the power
supply.
5. Fasten the SCSI disk with brackets to the terminal at the location of the pre-drilled
holes.
TELCO Ground Reference
Proper telephone interface operation requires a good ground reference from the chassis of
the Model 2100 or 2200 to the Telephone Company ground. You should run a heavy wire
(#16 AWG or larger) from one of the lower backplane Z-Bus mounting screws to the
telephone demarcation block ground point.
48 Vdc Ground Jumper
A jumper on the Z-Bus backplane (702-9071) labeled JP1 selects a floating or positive
ground referenced 48-volt telco power supplied by the Zetron equipment. When the
jumper is in position A, the positive (+) side of the 48V power supply is connected to
chassis ground; in position B, the 48V power supply is floating.
The default setting for this jumper is A, which gives the best results in most installations.
However, it may not be desirable to have the jumper in the “A” position when interfacing
to distant Central Offices. The slight amount of imbalance on tip and ring can introduce
some audio hum, which may be heard on the voice portion of a radio paging message.
Consult your Zetron Applications Engineer if you have questions.