ISSUE DATE: 10/01/09 

PROGRAM INFORMATION BULLETIN NO. P09-36 

FROM: LINDA F. ZEILER

Acting Director of Technical Support 

KEVIN G. STRICKLIN 

Administrator for 

Coal Mine Safety and Health 

NEAL H. MERRIFIELD 

Acting Administrator for 

Metal and Nonmetal Mine Safety and Health 

SUBJECT: Re-Issue of P05-05 - Use of Magnets near Remote Control Operated 

 Equipment 

Who needs this information?

Mine Safety and Health Administration (MSHA) enforcement personnel, underground 

mine operators, electrical equipment manufacturers, repair shops and independent 

contractors working at underground mines need this information. 

Why is MSHA issuing this bulletin?

An incident was reported in which a magnet caused a mining machine’s remote control 

unit to induce an unintended movement of the machine. The magnet was rated with 

strength of 190 pounds pull and was typically used to attach a methane detector bracket 

to a continuous mining machine. This device, commonly referred to as the “Gizmo,” 

permitted miners to take methane readings at the face areas of working places where 

extended cut mining was approved. 
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Unintended movement of remote-controlled equipment can pose a significant hazard to 

personnel. In order to evaluate the extent of this hazard, a survey was conducted to 

determine the type of magnets used in underground coal mines that use remotecontrolled equipment. The survey was limited to equipment where unintended 

movement would pose a hazard. The results of the survey indicate that there are 

various types of magnets used in close proximity to remote-controlled equipment in 

underground coal mines. These magnets vary in size, strength, and pole configuration. 

What needs to be done?

Permanent magnets, except for small magnets (e.g. pocket screwdriver-type), should 

not be used on any equipment in the same mining section as remote control equipment 

using Hall-effect switches unless the remote control system complies with one of the 

following two conditions: 

1. The remote control system requires a two-switch operation to produce machine 

movement. One of the switches, in this two-switch operation, must be a 

mechanical switch. Inactivity of both switches for a period of 5 seconds should 

require a new sequential operation. An example of this would be a mechanical 

tram enable switch with a Hall-effect tram switch. 

2. The remote control enclosure is designed so that a magnet placed anywhere on 

the outside surface of the enclosure will not affect the operation of the Hall-effect 

switch. 

 

In addition, the following remote control transmitters, commonly used to control 

continuous mining machines, were tested and evaluated with a determination of the 

acceptability of using each of these tested models in proximity to a permanent magnet: 

1. The Structured Mining Model TXCM100 has Hall-effect switches for the tram 

function on the remote unit but this system uses a mechanical switch to activate 

the tram function. This remote control system complies with Condition 1. 

Magnets can be used in the same section where this remote control system is 

operating. 

2. The Structured Mining Model TX942 remote control system does not use any 

Hall-effect switches. Magnets can be used in the same section as this remote 

control system. 

3. The Cattron Model C01MCMJ-1 remote control system does not use any Halleffect switches. Magnets can be used in the same section as this remote control 

system. 
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4. The Matric Type TX1 and the Matric P/N 603120-0035 (Plastic Station) remote 

control systems do not use any Hall-effect switches. Magnets can be used in the 

same section as these remote control systems. 

5. The Forced Potato Type U-XXX/L0KA01 has Hall-effect switches which operate 

the tram function and the cutting head function. This system uses a tram enable 

switch with an inactivity timer for the tram function. The inactivity timer can be 

programmed for 5 seconds. This complies with Condition 1. However, a second 

switch is not required to operate the cutting head function. Magnets should not 

be used in the same section as this remote control system. 

6. The Matric TX3 remote control uses Hall-effect switches and does not comply 

with either Condition 1 or 2. Magnets should not be used in the same section as 

this remote control system. 

For explanation of how magnets affect other remote control transmitters not specified 

above, please consult the remote control transmitter manufacturer. 

What is the background of this bulletin? 

Laboratory tests were conducted to determine the effect of magnets on the remote 

control systems from four manufacturers: Structured Mining models TXCM100 and 

TX942; Matric Ltd. Type TX3, Plastic Station, and Type TX1; Forced Potato Type UXXX/L0KA01; and Cattron Model C01MCMJ-1. The results of the tests follow: 

1. The permanent magnets tested can cause unintended operation of a Hall-effect 

switch of the type used on some remote control units. Magnets have no effect on 

mechanical switches. 

2. The permanent magnets tested do not interfere with the operation of the rest of 

the circuit. 

3. When spaced 1 inch or more from the surface of the enclosure of any of the 

tested remote control units, the magnets had little or no effect on any Hall-effect 

switch. 

What is the authority for this bulletin?

Federal Mine Safety and Health Act of 1977; 30 CFR §§ 75.520, 77.507, 57.12030. 

Who are the MSHA contact persons for this program information bulletin?

Technical Support, Approval and Certification Center 

Kevin D. Dolinar, (304) 547-2014 

E-mail: dolinar.kevin@dol.gov
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Coal Mine Safety and Health, Safety Division 

Salwa El-Bassioni, (202) 693-9525 

E-mail: el-bassioni-salwa@dol.gov
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Metal and Nonmetal Mine Safety and Health 

Safety and Health Division 

William W. Wilson, (202) 693-9640 

E-mail: wilson.william@dol.gov

Is this program information bulletin available on the Internet?

This bulletin may be viewed on the World Wide Web by accessing the MSHA home 

page (http://www.msha.gov) and choosing “Compliance Info” and “Program 

Information Bulletins.” 

Who will receive the program information bulletin?

MSHA Program Policy Holders 

Underground Mine Operators 

Electrical Equipment Manufacturers 

Repair and Rebuild Facilities 

Underground Independent Contractors 

Special Interest Groups 

Miners’ Representatives