because of flammable gases or vapors, flammable liquids, combustible dust,
or ignitable fibers or flyings, shall be rated and installed in accordance
with Chapter 5 of NFPA 70 and as shown.
1.4.2
Hazardous Environment
Components and wiring located in areas where fire or explosion hazards may
exist because of flammable gases or vapors, flammable liquids, combustible
dust, or ignitable fibers or flyings, shall be rated for the Classes,
Divisions, Groups, and suitable for the operating temperatures and shall be
installed in accordance with Chapter 5 of NFPA 70 and as shown.
PART 2
PRODUCTS
2.1
DATA TRANSMISSION EQUIPMENT
2.1.1
Modem
MODEMS shall be provided to allow mid-band-split, multidrop, polled,
asynchronous operation. MODEMS shall have the following general
requirements:
a. Mode:
Asynchronous half or full duplex as applicable.
b. Data Rates:
A minimum of 9600 bits per second.
c. Modulation Type:
Narrow band frequency shift keying.
d. Coaxial Cable Connections:
Standard BNC connector.
e. Error Rate:
Less than 1 error bit in 100,000 bits.
f. Operating Mode:
Multipoint or polled.
g. Test Function:
Local digital loopback.
h. Turnaround Delay:
Request to send / Clear to send (RTS/CTS) minus 8
milliseconds.
i. RF Output Power:
30 to 45 dBmv.
j. Transmit and Spurious Noise Levels:
50 dB below carrier.
k. Receiver RF Sensitivity:
Minus 15 to minus 10 dBmv minimum.
l. Interface Impedance:
75 ohms, unbalanced.
2.1.2
Taps and Splitters
Taps and splitters shall have a frequency response suitable for two-way
operation. All taps shall be of the directional coupler type. Isolation
between desired and undesired signal paths shall be 30 dB minimum. The
devices shall be designed for indoor or outdoor use as applicable.
Fittings shall be of the center conductor screwdown type and shall be
mechanically and electrically secure. All terminal installation material
such as cable fittings and grounding blocks shall be provided.
SECTION 16794A
Page 13
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