485FPP2595 - pg. 1/1
B&B Electronics January 1993
422/485 Fused Port Protector
Model 485FPP
Document No. 485FPP2595
Description
The 485FPP provides surge suppression for ports with RS-422 or RS-485 signal levels. In addition to surge
suppression, fast-acting fuses are used to protect the device against transient voltages too large or long in duration for
the device to suppress. The 485FPP was designed as a disposable device. Once a fuse is blown, the unit should be
replaced.
Installation
The 485FPP should be installed in-line with your existing wiring. The terminal blocks connect to your wiring, the
wire leads connect directly to your RS-422 or RS-485 equipment.
Four leads are provided on the 485FPP-two data lines, signal ground, and frame or green wire ground. (Note
that in four-wire communication systems, two 485FPPs are needed to protect four lines.) The yellow and blue wires and
the terminal blocks opposite of them are the data "A" and "B" (or "+" and "-") lines. Polarity is not important to the
485FPP, it is important that your "A" and "B" lines are not crossed from one side of the 485FPP to the other. The black
wire and its terminal block are provided for a signal ground connection. If you are not using a signal ground wire, this
connection is not necessary. The green wire and its terminal block are the frame ground connection. This connection
must be made or the 485FPP will not protect your port. At least one side (the green wire or the terminal block) must be
connected directly to a good frame (chassis, green wire, or earth) ground. This must be a low impedance connection for
the 485FPP to be effective.
Specifications
Surge Suppressers: 7.5 volt, bi-directional avalanche breakdown device. 500W peak power dissipation. Clamping
time < 1 x 10 -12 seconds (theoretical).
Fuses: 125 mA fast-acting type.
Series Resistance: 7.2 Ohms maximum.
Capacitance: 6000 pF maximum.
PDF 
ZIP