EST EST3X - Network data riser limits; Notification appliance signaling line circuit calculations

Appendix A: System calculations
232 EST3X Technical Reference Manual
Network data riser limits
Cumulative data network capacitance refers to the total capacitance of all copper
wire used for the data riser. The cumulative capacitance of data networks must
be within certain limits to permit stable network communications.
Audio networks are not affected by cumulative capacitance, due to the method of
retransmitting data. The audio network retransmits data byte-by-byte, so the
individual bit times of a byte are restored at each node in the network.
The data network retransmits data bit-by-bit. This method of retransmitting data
restores the amplitude of a bit at each node, but any distortions in bit timing are
passed through to the next node. Data network communication faults begin to
occur at about 23% distortion of bit timing.
Cumulative data network capacitance induces bit timing distortion.
A fiber link in a data network electrically isolates two nodes, but distortions in bit
timing are not restored by the fiber segment. Distortions in bit timing are passed
through the fiber to the next node. The bit transition time of model 3X-FIB8 and
3X-FIB fiber cards is fast enough to be neglected in determining the maximum
wire length that can be used in the data network.
Data network specifications
Here are the maximum allowed values between any three nodes of a network.
• Resistance: 90 ohms (Ω)
• Capacitance: 0.3 microfarads (µF)
• Distance: 5,000 feet
The following table lists the maximum cumulative capacitance for the entire data
network given various wire sizes and transmission rates. Maximum cumulative
capacitance is the total capacitance of all installed copper wire used in the data
network.
Maximum cumulative capacitance in microfarads
Wire size (AWG)
At 38.4 Kbaud At 19.2 Kbaud
18
1.4 2.8
16
1.8 3.6
14
2.1 4.2