621-9939C Honeywell Input module Brand new

Each controller uses a BACnet MS/TP communications 

port. The controller’s data is presented to other controllers 

over a twisted-pair MS/TP network, which uses the EIA-

485 signaling standard capable of the following baud 

rates: 9.6, 19.2, 38.4, 76.8, or 115.2 kilobits per second 

(configured at global controller). The Spyder BACnet 

controllers are master devices on the MS/TP network. 

Each Spyder BACnet controller uses a high-quality EIA-

485 transceiver and exerts 1/4 unit load on the MS/TP 

network.

Cabling should be selected that meets or exceeds the 

BACnet Standard which specifies the following: an MS/TP 

EIA-485 network shall use shielded, twisted-pair cable 

with characteristic impedance between 100 and 130 

ohms. Distributed capacitance between conductors shall 

be less than 100 pF per meter (30 pF per foot). Distributed 

capacitance between conductors and shield shall be less 

that 200 pF per meter (60 pF per foot). Foil or braided 

shields are acceptable. The Honeywell tested and 

recommended MS/TP cable is Honeywell Cable 3322 (18 

AWG, 1-Pair, Shielded, Low Cap, Plenum cable), 

alternatively Honeywell Cable 3251 (22 AWG, 1-Pair, 

Shielded, Plenum cable) is available and meets the 

BACnet Standard requirements 

(www.honeywellcable.com).

The BACnet MS/TP network is polarity sensitive. The 

maximum BACnet MS/TP network Bus segment length is 

4,000 ft. (1,219 m) using recommended wire. Repeaters 

must be used when making runs longer than 4,000 ft. 

(1,219 m). A maximum of three repeaters can be used 

between any two devices