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9.2.2
REQUIREMENTS FOR CONNECTION CABLES
Three types of cables are required:
1. The video cable, used to bring a standard composite video signal to the remote surveillance
station. Usually a 75 Ohm coax cable is used.
2. The power supply cable for the minidome THERA 5 (24Vac power supply unit). To define
cable dimensions, see "Power supply cables dimensions" in this manual.
3. RS485 cable, used for commands sent by the keypad to THERA 5. A 2-wire, twisted,
unshielded cable is needed. The suggested diameter is 0,64 mm (22AWG).
9.2.3
POWER SUPPLY CABLES DIMENSIONS
Pay attention to the correct dimension of the cable which provides 24V power supply voltage for THERA 5. If
the cable diameter is too little, the voltage dropout can cause malfunction. The following formula shows the
voltage provided to THERA 5 according to the cable dimension.
Where:
= Voltage on THERA 5.
V
D
= Transformer voltage.
V
T
= THERA 5 power consumption in Watt.
P
D
= Cable resistance in Ohm per meter (see the table below).
R
W
= Cable length (in meters) between THERA 5 and the power supply unit.
D
W
The following table shows the suggested lengths for the cable of a THERA 5.
DS1092-090
=
−
V
V
D
T
Wire diameter (mm)
2,60
2,05
1,63
1,29
1,02
0,81
0,64
Wire diameter and resistance values
Wire diameter (mm)
2,60
2,05
1,63
1,29
1,02
0,81
0,64
Power supply cable max. length
×
×
P
R
D
D
W
W
×
500
V
T
Resistance (Ohm/m)
3,35/1000
5,32/1000
8,46/1000
13,42/1000
21,36/1000
34,12/1000
54,14/1000
Cable max. length for outdoor
version (m)
200
125
80
50
30
20
10
58
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