Siemens FC700A - Manual (Page 16)

Bus systems
16
Siemens Building Technologies 007836_a_en_--.doc
Fire & Security Products 03.2004
6.2.1 Diagram
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20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440
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460 480 500 520 540 560 580 600 620 640 660 680 700 720 740
Radox
Lifeline
Standard
MICC
Rd [Ohm]
Ri [Ohm]
2. Procedure
Request characteristic impedance of the cable from manufacturer (45Ω ... 200Ω)
Select the value of the Ri the same as the value of the cable characteristic im-
pedance and insert the four end-of-line resistors on the p.c.b.
Insert two driver resistors Rd = Ri x 3.65 on the p.c.b.
Each C-Bus user must be adapted
If only the inductance and the capacitance are known for a cable, the impedance
can be calculated with the aid of the following formula:
Zc =
Lc
Cc Zc: Cable impedance [Ω]
Lc: Cable inductance [µH]
Cc: Cable capacitance [µF]
3. Mixing of different types of cable
In a C-Bus loop (or stub line) only one type of cable may be used.
4. Operation as a stub line
If the C-Bus is operated as a stub line, two end-of-line resistors (values as for Ri)
must be inserted externally at both ends of the line (default 110Ω). In the choice of
other cables the above rules apply (the Ri are in this case the external end-of-line
resistors).
For further information, see document 007831