In 2007, the New York Fire Department responded to 28,004 structural fires, 19,388 non-structural fires, 209,943 non-fire emergencies and 207,677 medical emergencies. FDNY relies heavily on approximately 15,000 remote fire alarm boxes placed throughout the city to alert it to the high number of situations that require its response. These boxes are the second most-common means of incident reporting, following 911 calls.

While using these boxes provides a fast and easy way to alert FDNY of impending disaster, maintaining the boxes and the potential faults in the system posed a different kind of problem for communications technicians.

New York is one of a number of cities in America to use the fire box, along with Sacramento, Calif., San Francisco and Buffalo, N.Y., as well as several smaller towns and cities. New York's first fire boxes were installed city-wide in the early 1970s, and many still are in operation today. These mechanical boxes use a spring-wound mechanism that, when pulled, opens and closes an electrical current, sending a coded number and box location to one of the city's dispatch centers. More recently, the city added Emergency Reporting System boxes that have buttons to notify the fire or police department specifically.

In October 2007, FDNY awarded Purvis a contract to modernize both types of boxes with digital technology, upgrading electronics and strengthening network connection. Once finished, the updated boxes will be backward-compatible with the current box structure, including redundant modular components to minimize box downtime and decrease repair time.

The boxes report to five dispatch centers in the city, divided by borough, via thousands of miles of underground telephone-grade, twisted-pair, copper cables. These cables are susceptible to the same problems that occur with standard telephone systems, including shorts, opens, splits, water ingress and intermittent faults. These problems can be caused by a number of factors, such as splicing errors, construction damage, standing water or general insulation degradation. If problems in these cables go undetected, the alarm boxes connected to them could cause delays in incident reporting, false alarms or even render the box completely inoperable.

Maintaining cable integrity, therefore, is paramount for FDNY's communications division, which identifies faults using insulation testers or voltommeters. While identifying faults is relatively easy, locating them is much more difficult. That's where Megger comes in.

Megger introduced FDNY to its CFL535F time domain reflectometer, a device that helps locate faults in the line quickly.

Before FDNY started using Megger's CL535F TDRs, technicians used a time- and labor-intensive method of finding faults. It involves dividing the distance of thousands of feet of cable, setting up a work area, pumping water out of manholes, opening cables, testing the circuit in each direction, breaking down the work area and then moving the operation in the direction of fault, only to repeat the entire process at the next location until the fault is located and repaired.

It can take as many as 10 setups before the problem is corrected. A time domain reflectrometer uses transmission line theory and pulse reflection principles to detect impedance changes along a cable. It transmits high-frequency electrical pulses that will travel through a cable until encountering a fault, at which point the pulse is reflected back to the TDR device and technician using it. The TDR measures the time it takes the pulse to travel back from the fault to determine the distance of the fault from the initial testing location. For FDNY, the dual trace capability of the CFL535F is an important time saver. Technicians use L1 on a known good circuit and L2 on a bad circuit, compare the wave forms side-by-side, and one or two possible problem locations stand out, significantly reducing the 10-plus setup locations. The more familiar technicians become with the TDR, the less time it takes to locate the fault along a specific cable.

The TDR pulse that appears on-screen also is representative of the type of fault in the cable. Typical signatures operators need to be familiar with are open or load coil, short circuit or ground fault, splice, bridge tap followed by end-of-tap, split followed by re-split, cross and wet section/water ingress. Understanding these symbols allows the technician reading the TDR to bypass splices and bridge taps and focus solely on the fault conditions.

The average cost of each TDR device is approximately $2,000, but the average cost of maintenance and repairs will vary from city to city. New York's 321 square miles require considerably more than a smaller city.

Megger helped FDNY communications technicians train on the time domain reflectometers and how to read the display, locate faults and determine distance. To help with training, FDNY simulated actual field conditions and situations for technicians to tackle.