Chapter 12 Communication Power Supply
12-4
12.4 Examining Power Supply Connection Positions
This section provides some suggestions for what can be done if the power consumption exceeds the maximum
allowable current value, using the following configuration as an example.
(Example 1) If the communication power supply is connected at the end of the network
Total power consumption value = 0.3 A + 0.1 A + 0.3 A + 0.1 A + 0.3 A + 0.2 A = 1.3 A
Maximum allowable current value = 1.03 A (from Figure 12.1)
From the summation above, it seems that the total power consumption value (1.3 A) is greater than the
maximum allowable current (1.03 A); i.e., the total power consumption value exceeds the maximum
allowable current.
(Action 1) Connect the communication power supply at the center of the network
Total power consumption value of section 1 = 0.3 A + 0.1 A + 0.3 A = 0.7 A
Total power consumption value of section 2 = 0.1 A + 0.3 A + 0.2 A = 0.6 A
Maximum allowable current value of section 1 = 2.01 A (from Figure 12.1)
Maximum allowable current value of section 2 = 2.01 A (from Figure 12.1)
In this configuration, the total power consumption is within the maximum allowable current value in
each section. Furthermore, it can be determined that power can be supplied to all the devices on the
network.
Device
Device
Device
Device
Device
Device
0.3A 0.1A 0.3A 0.1A 0.3A 0.2A
300m
Trunk line (thick cable)
Termination
resistor
Termination
resistor
Communication
power supply
150 m (section 2)
150 m (section 1)
Device
Device
Device
Device
Device
Device
0.3A 0.1A 0.3A
0.1A 0.3A 0.2A
Termination
resistor
Termination
resistor
Trunk line (thick cable)
Trunk line (thick cable)
Communication
power supply
