Toa TS-800 Series Operating Instructions Manual page 52

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
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
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.
RG-59/U
RG-6/U
RG-11/U
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
RG-6/U
RG-11/U
52
= 0.841 V
= 0.513 V
73 m
77 m
154 m
73 m
77 m
114 m