Honeywell TB7600 Integration Manual page 5

Maximum Cable Length
The maximum length of a chain is related to its transmission speed. The longer the chain, the slower the speed. Using proper
cable, the maximum length of an EIA-485 daisy chain is 4000-ft (1200 m). This will only work reliably for data rates up to 100,000
bps. TB7600 themostats' maximum data rate is 76,800 bps.
If you require a maximum network length of more than 4000 feet, then repeaters are required to extend the network.
EIA-485 Repeaters
If you have more than 64 devices, or require a maximum network length of more than 4000 feet, repeaters are required to extend
the network. The best configuration is to daisy chain the repeaters to the controller. From each of these repeaters, a separate
daisy chain will branch off. Fig. 3 demonstrates a valid use of repeaters in an EIA-485 network.
Do not install repeaters in series, as this may result in network reliability problems. Fig. 4 demonstrates an incorrect use of a
repeater in an EIA-485 network.
Fig. 4. Incorrect usage – the second repeater in series may result in an unreliable system.
BACNET INTEGRATION MANUAL FOR TB7600 SERIES THERMOSTATS
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Fig. 3. Correct usage – repeaters are daisy-chained to the supervisory
controller and separate daisy chains branch from each repeater.
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REPEATER
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