Loop Current Attenuator


The Loop Current Attenuator reduces potentially damaging loop current to an acceptable level without sacrificing the voice or data quality of a circuit.


The Loop Current AttenuatorĀ is a very economical solution for protection of expensive terminal equipment!

The Only Network Balanced Loop Current Attenuator, ITC-4001 Just Got Better!
Now with 2 Female Modular Jacks AND Terminal Wires. Easy for Punch-downs or Screw Terminals!

Excessive Loop Current is a Growing Problem! Too Much Loop Current may cause those “phantom” problems such as:

  • Intermittent Garbled Data
  • Cut-offs
  • Squeals
  • Echoes
  • Hollow Sounds
  • …and other failures due to no apparent reason.

Combine electronic exchange or PABX offices, with electronic terminals and the result is often:

  • Burned out key & PABX circuit packs
  • Damaged networks in Modems, Fax Machines, Electronic Telephones, Personal Computers, …or any electronic terminal.

Coin Telephone Networks can be “Cooked” by High Loop Current

  • Use the ITC-3004-Kit (Loop Current Test Set) to easily identify loop current problems.

Learn more about the Loop Current Issue…

With the installation of new central offices, miles of fiber cable and repeaters, loop current is becoming a frequent customer problem. (The optimum range for loop current is 23 to 35 milliamps – MA.)

We are finding abnormal loop current in a wide variety of situations. Here are some examples:

  • One of the leading suppliers of electronic Key telephone systems migrated their trunk circuit packs into a new technology. To everyone’s surprise, trunk packs in several exchanges experienced only 50% service life. The mystery was discovered to be excessive loop current (over 60 MA).
  • An interconnect and service company in North Central New York had one particular
  • line of key systems that gave them trouble for months. It was an electronic type A2 key system that was plagued with short lived central office circuit packs and erratic sound. Excessive loop current was found to be the problem.
  • In a suburb of a large southern city, a large number of electronic Key /PABX systems and other terminal equipment were experiencing “phantom” troubles, such as cutoffs, modem failures and circuit pack burn up, etc. The problem was due to an excessive increase in loop current after the local telephone company cut-in a new fiber optic feeder cable.
  • An alternate common carrier utilizing a bank of over 80 dialers for automatic” call forwarding” was plagued by “mystery” failures in dialer software. Dialers would “lock- up” and simply not function. Never all at once, but one time or another and almost weekly. The problem was central office trunks delivering from 50 to 69 MA (within FCC guidelines
  • The dialer manufacturer said their dialer networks were protected to 70 MA. When the loop current was reduced within the 25 to 35 MA range, the “mystery” disappeared.
  • Payphone service personnel have experienced intermittent failures in the electronics of their “smart sets.” Often this is the result of excessive loop current. Too much loop current can “cook” a telephones electronics and cause immediate failure or at a minimum shorten component life by constant exposure to higher than necessary loop current. The Loop Current Attenuator will protect and dramatically increase the life of the payphone electronics.
  • Standard public telephones are not immune from such problems. Excessive loop current can affect transmission causing such things as howling on the line, interference with volume controls, hearing aid compatibility, etc.
  • A large southwestern airline discovered that loop current was the cause of on-going trunk problems. The airline repeatedly attempted to get the telephone company and PBX manufacturer to resolve the problem. Finally their own in-house technicians attenuated the hot CO trunks. The Telco and manufacturer never did get together.
  • A business in Arlington, Virginia served by a mid-sized electronic PBX experienced frequent cases of “can’t send” on fax machines behind the switch. The “switch” lines were measured and high loop current was determined to be the culprit. The ITC-4001 solved the problem.
  • Another firm in the same city was losing electronic features on stations with long or off- premises cable runs. The problem in this case was inadequate loop current.
  • In North Carolina a business was experiencing a loud intermittent squeal on one of its Watts lines. Four line cards and 65 maintenance hours were invested before discovering fluctuating loop current ranging from 36 to 52 milliamps.
  • A marginal loop current of 19-20 milliamps was responsible for a long distance switch ! not recognizing the 213 area code in the Los Angeles area.
  • In Maryland, a repairman was frustrated by repeated reports of crosstalk on a particular foreign exchange (FX) line. After replacing several defective line packs in the KTU, high loop current was determined to be the problem. The constant high current would eventually break down the line pack and crosstalk would return.

Additional information

Weight .15 lbs
Dimensions 3 × 2 × 1 in