COMMUNICATION SYSTEMS RESEARCH AT 

BRUCETON SAFETY RESEARCH MINE 

Howard E. Parkinson 

Supervisory Electrical Research Engineer 

U.S. Bureau of Mines 

4800 Forbes Avenue 

Pittsburgh, Pennsylvania 152 13 

ABSTRACT 

An environment monitoring and communication system has been installed in the 

Bruceton Mine, and research is under way to improve mine safety. Standard day-to-day 

mine communications are available, along with additional systems installed to permit 

experimentation with wireless radio, through-the-earth phones, along-the-roof paging, and 

mine face machinery communications. 

Research is continuing and the essential concepts for a dependable whole mine 

comnlunication system, providing simple environment monitoring, improved day-to-day 

communications and post-disaster comn~unications, will be demonstrated in a larger mine 

with about 900 feet of overburden. 

INTRODUCTION 

Some fifty years ago the U.S. Bureau of Mines experimented with seismic and 

electromagnetic mine communicati'ons. The experimentation closed with the thought that 

electromagnetic communications had promise as ;a means of co~nmunicati~lg through the 

earth. 

During the early- and mid-1940's, the U.S. Bureau of Mines experimented further with 

electromagnetic communications. The experimentation resulted in the development of 

trolley wire communications for mine motors. 

In 1969 the Federal Government enacted coal mine hc:ilth and safety legislation. 

Followil~g the enactnlent, the Bureau of Mines co~ltractccl conlm~~l~ications research. An 

in-house reser~rch prograxn was started in 1970. During 197 1 the I~ldt~strial l-Iazards and 

Conlm~~tlicatiolls group was formed and mine con~n~unicatiolls research is now a cooperative 

effort of ul?ivcrsities, private industry, the coal industry, other governmental agencies and 

thc Dureau of Mines. 
' PRESENT COMMUNICATIONS 

The present mine telephone and trolley phone systems (Table 1) provide for vital 

operational efficiency. The coal industry has recognized this, and has accepted amplified 

telephone equipment that extends the selective area ring into individual paging and provides 

communications to the mining section. The industry has also accepted the trolley phone, an 

ingenious device that aids in expediting rail haulage. 

TABLE 1 

PRESENT SYSTEMS 

Medium Typical Equipment Uses 

Telephone Line 

Trolley Wire 

and Rail 

Hoist Ropes 

Power Lines 

Magneto Phone Fixed Stations 

Amplified Phone Dispatcher to Mine 

Sections and Shops 

Carrier Phone 

88- 100kHz 

Mobile 

Dispatcher to Motors 

Carrier Phone Cage to Hoist operator 

88-1 00kHz 

Carrier Fan Monitor and Circuit 

Breaker Control 

However, mine communications are still plagued by the problems of broken lines due 

to roof fractionation and the opening of temporary splices, and the problem of not being 

able to reach the vital operating extremities of the mine. These problen~s not only affect 

mine operational efficiency, but inhibit the maintenance of safe operating practices. 

COMMUNICATIONS OBJECTIVES 

To maintain safe operating practices, general mine communications must encompass 

post-disaster rescuing, environment monitoring, and day-to-day operating communications 

as an integrated whole (Figure 1 ). 

4 

Whole Mine 

Communications 

for 

Safety 

and 

Efficient 

Operat ion 

w 

FIGURE 1 A NEW PERCEPTION OF MINE COMMUNICATION SYSTEMS 
The day-to-day operating mine communications must help achieve the following 

objectives: 

To know the working environment is safe 

To assure efficient and safe mine operation 

To provide communication in rescue operations 

The Bureau has "fire-truck" type equipment which has been deployed to determine 

the conditions of the in-mine environment and to provide seismic and electroinagl~etic 

comlnunicatioils during rescue operations. The response tinle limits the effectiveness of the 

"fire-truck" concept. 

Recent post-disaster rescue efforts have brought into focus the simple fact that rescue 

operations involve more frequently the recovery of bodies rather than the rescuing of 

miners. What more beneficial uses can be envisio~zed for post-disaster con~murzications? 

First, novel ideas used in post-disaster communications can be integrated into day-today operations to overcome the weaknesses of 

existing day-to-day communication,s. 

Improved day-to-day mine comm.unications systems can, in turn, 

provide instant post-disaster co~nm~unications. 

Finally, environment monitoring from the surface via the mine 

communications systems can be used to anticipate and prevent 

disasters. 

Having perceived these three potential benefits, the Bureau is evaluating and demonstrating a number of communications concepts for economically providing the desired 

improved mine communications. 

CONCEPTS FOR IMPROVEMENT 

Telephone and trolley phone systems are limited. Most phone lines are extended as the 

inine extends. The longer the phone line, the more difficult it is to reach the last station and 

the more likely the line will be broken by a small "'roof fall" (Figure 2). 
 Selector 

0 A 

v 

Dispatcher Phone 

.; .:.: *,>';,;, 

:.:.-A? .:t,' 

..... .. :. . !. ... ... .. 

I A 

Phone Line 

I v I @ In-Mine Phones 

FIGURE 3 LOOPED PHONE SYSTEM 

Each message going into the mine also comes out. If the message is not receive

surface phone can be switched to the overland line and an effort made to reach thc in-

phones. Since signals can be provided to each side of a break in a phone line, 

munications are not necessarily interrupted by a break in a line. 
1 

I 1 I 

FIGURE 4 SELECTIVE PATHING COUPLER 

Looping and selective pathing are things that can be done. Ilorvever, other ex

mental activities also have immediate promise. 

Through- the-Earth Communications 

Through-the-earth paging by amplified pager-telepl~ol~e output (Figure 5) has 

demonstrated through 1,700 feet of overburden. Amplified pager output was connected 

grounded dipole through an impedance matching transformer. A galvanic current circu

tlirough the various layers of overburden, ancl a signal was received on a small ferri tc loo

a "manpack" receiver. In another experiment, the signal voltiige was taken from two 

bolts, amplified, and placed on the mine telephone line to be received in the telep

handset. 
y 

the receiver amplifier being connected to a third roof bolt. The range was checked out 

up to 600 ft of overburden. The system provided two-way voice communications. 

Received Signal 

1 

n ?.p?.:..i.::;-;s; ;:;p:::='..?.;:.:< >:.%:'..:.:" ::::. .:; x.,; :: ::y;,-.:, .;::;>: :.: ,~i5:~4.47v,:: ..-.->..: :2;;$;c;2;c,,.,:::,.: :,* ;,:;{. ;:; ....-. ,>.;, ..:-. .2..7: , , ;.. .: >;,:>:<:;:<;$:>; . . .,: :.-1. .... L. . # . 

Speaker Trolley t_<l I 

n Phone A Received Signal I 

Transmitted Signal 

FIGURE 6 THROUGH-THE-EARTH TROLLEY PHONE 
is far removed from the face, and the face area is noisy. In scveral experiments a stan

trolley phone with the signal connected to two roof bolts provided an electromagnetic 

along-the-roof, and the page was received throlughout the section (Figure 8). A 

contained pocket pager was modified to receive an 88kHz signal. 

Roof Bolts 

: /.,. i: -:., ; .:.. v.:::...: T.:;:~y;i.:,.:.,;y,?:. '.;.'.'.'.:f .! ::r::;:-. .. . 

., ,. ;- .,. ,.;; ......>::::..' . , . ,< , , > . : .-;:~;.;.;:{:;::;,. .-.....A. ::.:-:' :'.'.

Converter-Loudspeaking 88 kHz Pocket Pager 

Phone to 88 kHz Section 

Foreman 8: ... . >...'. '.-. 1 . "". :,>-:,,,-7..:. ;:;:.. ' , ' .'...".'.' .. . . ..,;.:;; !:.,; ::,:;..,:.:;: .-',:-.,.:.,*; .-,.,": ',.. ....,. , :.:.-. >...*.,;,.- . 

..>: ~:;;ir;~;;r'*iI~~>;~!;;;;I';:;~.;~:;;2. .,.;-:;:. ;'-i:;;;i;; .:,.7.f.,:-. . ,; 1:. , , ,. , . . ... , . ,, , , .;.:.;..: . ..:,;. "'.( '.'i"..~::'..:'.-~

-.-.... ...>.. .... -::!.y ,^.I::.-,.. I; .,... v.:..-..<:: . . ...:.:..:..;..;::,.~.~_; ,.:,; -.,. \.. .!. ..-. -. .. . '* .Ti.-.'.... . ..,.-. .- ...... .... . _ . .-,. .*-' 

FIGURE 8 ALONG-THE-ROOF PAGING 
,-.. :;,;:~<$;~$~~$(.+;~;~.; ..... :...;a . , . .. . .i'"'". !;v::.:,..* ..' . .-; ..& ,,.*;, 

...-. LC ..... '. 

FIGURE 9 POWER MAIN AND FACE MACHINERY TRAILING CABLE METHODS 

Though it has not been tested, an AC continuous miner could communicate with 

shuttle car. Permissibility for 1 2V equipment is anticipated. 

Another project extends the permissible pager to a face machine. Modified tra

cable includes a twisted pair of #18 wires. The section pager line will be connected t

trailing cable phone line. The manufacturer indicates the cable presents no unusual man

turing problems. 

Guided Wireless Radio 

Some of the projects indicate that quick returns can be anticipated by adap

selected ideas into day-today mine colnmunication systems. Others require a compl

new mine communication system. During the Sunshine Mine postdisaster rescue opera

465mHz wireless radio was used (Figure 10). The signal was guided by a small g

insulated wire droppsd on the mine floor. Non-line-of-sight commu~iications were e

lished at a distance of 2,300 feet between two portable units, and with one portable 
300 feet from the wire. Extensive experimenting is being done with guided wireless radio. 

B - Base Station 

GL - Guiding Line 

ZR - Matched Load 

MI, M2 - Mobile Sets 

FIGURE 10 GUIDED WIRELESS RADIO 

The experimenting is not yet conclusive as to the desired frequency or type of guide. 

Three frequency ranges, 27mHz, 17OmHz, and 406mHz to 4GOmHz have been tried. Studies 

also indicate that even higher or lower frequencies -might have advantages. The guides we are 

experimenting with are a simple insulated wire terminated to a roof bolt col~nection, an 

inexpensive coaxial cable terminated in 70 ohms, a special heliax cable, and a specially 

designed quasi-antenna spaced throughout the length of a coaxial line. Our experiments have 

resulted in the development of a special in-mine repeater that greatly extends the range of 

the base station to the portables. The guided wireless radio system can provide communications between surface and motor, surface and section, and between two roving miners. A 

surface radio loop-back has also been established by an overland 40GmHz radio link. By 

multiplexing, all in-mine monitoring, pager, trolley phone, and wireless radio sigl~als are 

being looped back to the mine foreman's office. 

Some essential benefits and costs of the phone systems discussed are summarized in 

Table 2. 

TABLE 2 

SYSTEM CONCEPT EVALUATION 

Or1 Unit of Equipment Cost 

0:1 Unit of Line Cost 

0 No Cost 

t 

System 

Telephone 

Trolley Phone 

Radio Phone 

1 

Relative Cost 

Equipment 

l 

UOhl 

-- 

El 81 q 6 Yes 

Line 

0 

@ 

to 

Function 

Fixed 

to 

Fixed 

Yes 

Yes 

Yes 

Effectiveness 

Fixed 

to 

Motor 

No 

Yes 

Yes 

Hard 

Wired 

Good Very 

Good 

Not 

Good Good 

Guided 

Good Not 

OK 

Good I 

Through 

the 

Earth 

Good 

OK 

Not 

Motor 

to 

Motor 

No 

Yes 

Yes 

Along 

the 

Roof 

OK 

Good 

Not 

Between 

Roving 

Miners 

IJ o 

No 
BRUCETON INSTALLATIONS 

The communications systems installed in the Bruceton Safety Research Mine are aimed 

at developing an emergency communication system, based on available technology, that is a 

practical extension and modification of existing general-purpose mine communications 

equipment. Table 3 is a list of some of the sub-systems operating or being installed at this 

time. 

TABLE 3 

SUBSYSTEMS-BRUCETON SAFETY RESEARCH MINE-OPERATING OR BEING INSTALLED 

Mine Monitoring - 10 Major Locations 

Mine Paging Telephones - Main Operating Points 

Monitor-Trapped Miner Locator - Communicator Station - 3 Fixed Locations 

Sou ndpowered Telephones - Explosion Test Area 

Telephone Through-the-Earth Paging - Throughout Mine 

Power Cable Telephone - Face Machine 

Public Phone System Tie to Mine Paging Telephones -Telephone Building 

Battery Operated Motor - Haulage Communications 

Trolley Phone Along-Roof Paging - Working Section 

Pilot-Wire Power Cable Trolley Phone - Face Machine 

Through-Earth Trolley Phone - Fixed Rescue Point 

Overland Power Line Carrier - Office to Mine Section Borehole 

Loop Back on Power Line Carrier 

Haulage Communications 

Wireless Radio - Main Operating Areas 

Overland Radio - Foreman's Office to Mine Section Borehole 

Loop Back on Overland Radio 

Haulage Communications 

Mine Paging Telephone 

Wireless Radio 

Mine Monitoring 

The Mine (Figure 11 ) is a gathering point of a variety of systems for the purpose of 

evaluating and demonstrating the preceding concepts. The concepts are iinplemented with 

the goal of providing system confiyratioiis that will permit instant communications du~ing 

an emergency, togzther with providing both operatior.;!l communications and continuous 

monitoring of the underground environment. The basic systems-engineering details of the 

Bureau of Mines cxperimental work will be covered in future articles. Details of environment monitoring and other communication concepts will be given by several participants in 

this conference.