Toa TS-800 Series - Manual (Page 52)

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2) Finding the maximum cable length using voltage drop
The current flowing from the Distributor 2 into each coaxial cable connected to the TS-905 Infrared
Transmitter/Receiver unit is 0.1 A, since the number of Infrared Transmitter/Receiver units connected to
each coaxial cable is 1.
Assuming that RG-59/U coaxial cable is used, the voltage drop between the Distributor 2 and the Infrared
Transmitter/Receiver unit is calculated by the following equation:
Voltage drop = 16.82 Ω x (50 m / 100 m) x 0.1 A
= 0.841 V
When RG-6/U type coaxial cable is used, since the current flowing into each coaxial cable between
Distributor 1 and Distributor 2 is 0.4 A, the voltage drop between the two is calculated by the following
equation:
Voltage drop 2 = 12.82 Ω x (10 m / 100 m) x 0.4 A
= 0.513 V
Voltage drop 1 + Voltage drop 2 = 1.354 V
A remaining voltage of 3.646 V (5 V – 1.354 V) is the maximum allowable voltage drop between the
Central unit and the Distributor 1. The current that flows between the two is 1.6 A.
• Assuming that RG-11/U coaxial cable is used, L1 between the Central unit and the Distributor 1 is
calculated by the following equation:
L1 = { (Voltage drop 1 / Current 1) / Coaxial cable loop resistance 1 per 100 m }
= { (3.646 V / 1.6 A) / 2.4 Ω } x 100 m
= 94 m
Maxim cable length L (Length between the Central unit and the Infrared Transmitter/Receiver unit)
= 94 m + 10 m + 50 m = 154 m
• Assuming that RG-6/U coaxial cable is used, L1 between the Central unit and the Distributor 1 is
calculated by the following equation:
L1 = { (Voltage drop 1 / Current 1) / Coaxial cable loop resistance 1 per 100 m }
= { (3.646 V / 1.6 A) / 12.82 Ω } x 100 m
= 17 m
Maxim cable length L (Length between the Central unit and the Infrared Transmitter/Receiver unit)
= 17 m + 10 m + 50 m = 77 m
Similarly calculated for other types of coaxial cables, the maximum cable length between the Central unit
and the Infrared Transmitter/Receiver unit is found in the following table.
The table below shows the required maximum cable length for the example 4, the shorter length of the
calculation results (1) and (2) above.
RG-59/U 73 m
RG-6/U 77 m
RG-11/U 154 m
RG-59/U 73 m
RG-6/U 77 m
RG-11/U 114 m