Envoy 1-4 Zone Conventional Fire Alarm Control Panels Specifications download pdf (Page 91)

Diagrams are for reference only.

Consult the appropriate installation sheet for wiring details.

NETWORK DATA RISER LIMITSNETWORK DATA RISER LIMITS

NETWORK DATA RISER LIMITS

REFERENCE SECTION

Overview

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 3-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 • Distance: 5,000 feet

• Capacitance: 0.3 microfarads

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

Cable properties

Data and audio networks in an EST3 system do

not

require the use of shielded cable,

and networks designed with twisted-pair can be about twice as long as those designed

with shielded cable. The maximum length of a data network varies with the properties

of the wire used. Wire manufacturers typically provide specifications for wire resistance

and capacitance.

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