GAI-Tronics 758-002 User Manual
Pub. 42004-260C
GAI-TRONICS® CORPORATION
A HUBBELL COMPANY
Model 758-002 24 V DC Weatherproof
Speaker Amplifier Enclosure
Confidentiality Notice
This manual is provided solely as an operational, installation, and maintenance guide and contains
sensitive business and technical information that is confidential and proprietary to GAI-Tronics. GAITronics retains all intellectual property and other rights in or to the information contained herein, and
such information may only be used in connection with the operation of your GAI-Tronics product or
system. This manual may not be disclosed in any form, in whole or in part, directly or indirectly, to any
third party.
General Information
The Model 758-002 Weatherproof Speaker Amplifier Enclosure is an important component of the 700
Series Page/Party System. It is constructed of cast aluminum alloy, which is extremely weatherproof
and corrosion-resistant, and can be used in either indoor or outdoor applications.
This enclosure is designed for 24 V dc input systems, and is equipped with terminal strips for connecting
inter-station system cable. The GAI-Tronics Model 751-002 Speaker Amplifier mates directly into this
enclosure.
Installation
CAUTION
indicated on the approval listing in the “Specifications” section of this manual. Such installation
may cause a safety hazard and consequent injury or property damage.
When installing an add-on station, consult the 24 V dc system layout diagrams at the end of this manual.
These figures, when used in conjunction with the station installation information and cable layout guide,
should provide all the information necessary to install additional Page/Party stations.
In 24-volt systems, plan on several branch lines from the dc source with no more than six stations per
branch. One branch could span up to 4,000 feet for a single station. The Maximum Cable Distance
Table lists the limits. Where two or more stations are listed, the assumption is that they are evenly
spaced along the cable.
Each amplifier contains two fuses on the PCBA in the 24 V dc input to protect and isolate the handset
and speaker amplifier circuitry in the event of a failure. Power line wiring to each amplifier or group of
amplifiers should have a fuse or circuit-breaker to protect against wiring failures.
Do not install this equipment in hazardous areas or areas other than those
GAI-Tronics Corporation 400 E. Wyomissing Ave. Mohnton, PA 19540 USA
610-777-1374 800-492-1212 Fax: 610-796-5954
ISIT WWW.GAI-TRONICS.COM FOR PRODUCT LITERATURE AND MANUALS
V
Pub. 42004-260C
Model 758-002 24 V DC Weatherproof Speaker Amplifier Enclosure Page
If cable with No. 14 AWG power line conductors is used, a 15-amp fuse or circuit breaker should be
installed for each branch line at the point it connects to the battery. Fuse or circuit breaker rating is
determined by the size cable used in the branch. Consult the National Electrical Code (NFPA70) or
Canadian Standards Association (CSA 22.1) for the maximum allowable capacity of the wire used.
®
The GAI-Tronics 24 V dc series of Page/Party
system equipment is designed to operate from a 24-volt
dc rechargeable battery. A battery charger may be connected to the battery to maintain the charge.
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CAUTION
Under NO condition should this equipment be operated from a battery
charger without the batteries connected.
Most chargers have an unloaded output of 35 to 45 volts that can quickly damage the equipment designed
for nominal 24 volts. To maintain a proper state of battery charge, the voltage across the batteries will be
somewhat greater than 24 volts, but should never exceed 28.8 V dc. Grounding the negative side of the
battery system at only one point is recommended and will ensure hum- and noise-free operation.
Enclosure Placement
All GAI-Tronics Page/Party® units are wired in parallel. Good system layout design minimizes the cable
required for each installation. GAI-Tronics multi-conductor cable, designed especially for this
application, is recommended. The number, size, and color-coding of conductors are listed in the
accompanying system connection diagrams.
System layout and power cable length are important considerations when installing Page/Party
equipment. Consult the Maximum Cable Distance table for typical cable lengths. The cable distance
between stations as well as total cable distance must be considered. Cable distance is more strictly
regulated in 24 V dc systems because of the amount of resistance these cables encounter—the longer the
cable distance, the greater the resistance and IR losses (voltage drop) encountered.
®
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Pub. 42004-260C
Model 758-002 24 V DC Weatherproof Speaker Amplifier Enclosure Page
Maximum Cable Distance in Feet*
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Number of
Units
No. 14 AWG
Total / Between
No. 12 AWG
Total / Between
No. 10 AWG
Total / Between
No. 8 AWG
Total / Between
1 977 / 977 1,554 / 1,554 2,471 / 2,471 3,931 / 3,931
2 651 / 325 1,037 / 518 1,648 / 824 2,620 / 1,310
3 489 / 163 777 / 259 1,236 / 412 1,966 / 655
4 391 / 98 622 / 155 988 / 247 1,572 / 393
5 325 / 65 518 / 103 823 / 165 1,310 / 262
6 279 / 46 444 / 74 706 / 117 1,123 / 187
9 196 / 21 311 /34 494 / 55 786 / 87
*Based on the following assumptions:
Continuous tone (alarm) signals driving each station’s speaker amp to a maximum of 12 watts.
N
OTE: If the station is used for speech (audio) signals only, the distances stated above can be
multiplied by a factor of 2 because speech signals do not have the energy content that a
continuous tone has; therefore, they do not require as much average current and thus less cable IR
drop will result.
GAI-Tronics-supplied cable is used.
Wire resistance (ohms) is the nominal value for the applicable AWG at 1,000 feet of bare copper,
stranded wire @ 20º C (68º F). Wire resistance values used are as follows:
No. 14 AWG = ~2.525 ohms; No. 12 AWG = ~1.588 ohms; No. 10 AWG = ~0.999 ohm; No. 8 AWG = ~0.628 ohm
DC V at cable run’s feed point (Float charge of connected batteries) = ~26.6 V dc
DC V at the last unit in cable run = 21 V dc minimum
Station unit current draw (I) is the same regardless of the unit’s placement along the cable run for
ease of calculation. (1.1 amperes when unit is producing a 12-watt sine wave output.)
Distances reflect a 3% reduction for margin of error.
For conditions other than above, the following formula may be helpful in calculating the approximate
maximum distance for a SINGLE station.
For CONTINUOUS tone applications
For SPEECH operation only
, multiply the above result by a factor of 2.
with minimum distortion:
Example: What is the approximate maximum distance for a single dc station if the voltage feed is 27.5
V dc and a No. 14 AWG wire is used @ 20º C?
Info:
No. 14 AWG @ 20º C = ~0.002525 ohm per foot 2 for LOOP R
V
FEEDPOINT
= 27.5 V dc
Solution:
(27.5 V – 21 V) / ((2 0.002525 ohm per foot) 1.1 amps)
= 6.5 / 0.005555
= 1,170 feet (for CONTINUOUS TONE
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signal), or up to ~2,340 feet (factor of 2) for SPEECH signals
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