Model TW-6 Split Box Pipe & Cable Locator, by Fisher

Uses transmitter and receiver to locate underground metal objects such as pipes, cables, manhole covers, vaults and valve boxes.


The well known Fisher M-Scope Model TW-5 Pipe and Cable Locator was upgraded in performance and user friendliness to the Model TW-6. The new model performs the traditional finding tasks of locating underground metal objects such as pipes, cables, manhole covers, vaults and valve boxes.

The TW-6 like earlier models will be primarily used by water departments, telephone companies, electric power companies, gas companies and petroleum pipeline companies to know where to dig, and sometimes more importantly where NOT to dig in making repairs or rearranging buried lines.

The substantial increase in sensitivity of the TW-6 required that we remove all unnecessary metal parts. They collectively inhibited the tracing distance of the more efficient locator. That is why the new very durable catches holding transmitter and receiver together as well as the individual carrying handles are now completely non-metallic. The familiar aluminum loop antennas on the TW-5 and earlier models have been replaced by actual coil windings around the edge of the underside of the face panels on the transmitter and receiver. This change along with the completely upgraded electronics has boosted the tracing performance 50-100%.

Longer tracing which used to require expensive high powered fault locator/tracers can now be accomplished very economically. 


  • Tracing distance increased 50 to 100%.
  • Crystal controlled frequency in both transmitter and receiver. This keeps both transmitter and receiver precisely on the same frequency for longertracing distance.
  • VCO (Voltage Controlled Oscillator) gives a much wider range of signal to indicate the presence of metal. Even after the meter pegs, the sound goes much higher in pitch and volume in response to signal strength.
  • Specific noise canceling circuitry has been added to eliminate power line interference.
  • The TW-6 is powered by eight (8) standard AA (pen-light) batteries in the transmitter and in the receiver. An optional rechargeable Ni-Cad battery kit is available with the same number of batteries and a charger.
  • At 5-1/2 lbs., the TW-6 is 1.5 lbs. lighter than the previous Model TW-5.


The TW-6 is Versatile

Many locators for underground pipes and cables can only trace from a known starting point, however it is the "two-box" M-Scope invented by Fisher in 1931 that made totally inductive location a reality. The TW-6 is a direct descendent of Dr. Fisher's 1931 invention. When you have no starting point for placing the transmitter, this is the only way to locate deeper pipes, cables and other metal items. Non-metallic pipes may be located inductively or conductively if conductive tracer tape or wire is placed in the trench above the line.

Inductive Locating

Using a four foot handle, you have the transmitter behind you and the receiver ahead, while walking a pattern to discover buried metal objects. The locations become known from meter movement and speaker sound. The ground or pavement is marked for each sensing so that soon a pattern emerges of underground linear objects such as pipes and cables, or separate items such as a buried manhole cover.

Inductive Tracing

When one point is known on a linear conductor such as a pipe or cable, the transmitter portion of the TW-6 can be placed over it and tracing can go in either direction from that point. You then walk out the path of the line and "wag" the receiver left and right over the line. At a distance from the transmitter, the signal will become faint but the transmitter can be brought up to that point so tracing can continue to the end of the line.

Conductive Tracing

Conductive tracing is the preferred method for tracing because the transmitter makes a direct physical hook-up with the line to be traced. The included ground plate assembly plugs into the transmitter with one wire going to an alligator clamp to be attached to the pipe, non-energized wire, or conduit. This concentrates the signal on the known line to be traced and there is less chance of the signal being induced to a nearby or adjacent line to cause confusion. Tracing distances are increased 25-50% over the inductive method. Non-metallic pipes may be traced conductively if the ground plate assembly is attached to a plumber's "snake" or electrician's "fish tape" running inside of the pipe.