Install of the Month
May 1, 2002 12:00 PM, NAT HECHT
Intercoms have to withstand the toughest of conditions — the Big Apple's morning commute
TRAVELING ON New York City Transit (NYCT) can be a daunting experience for the uninitiated. With 468 stations and numerous lines serving all four of the city's boroughs, the system's jostling crowds, trains, ambient noise and shifting schedules can result in a kind of subway roulette. To enhance the level of customer service, the NYCT has introduced a new subway car called the R142. Designed to be faster and quieter than its predecessors, the R142 has contemporary digital audio and sign systems to provide clear identification of train routes and destinations.
The new car features clear voice announcements inside and outside through two emergency panels located near each door. The car has electronic strip maps that indicate direction of travel and the next station, pressure-sensitive doors to prevent objects from being caught, dedicated wheelchair space and high-efficiency diffused lighting. Intercoms designed and produced by the Telephonics Corporation of Farmingdale, New York, provide emergency communication between the crew and passengers.
The heart of the R142 subway car P.A. and signage system is the Telephonics Communications Management and Control (CMC) unit, a powerful computer-controlled digital audio processing and switching device. Using system control and distribution functions that are largely implemented in the computer software itself, the CMC offers a high degree of flexibility and supports evolution of the system to address changing NYCT customer service needs. Also contributing to the project was Optim Engineering of Norwalk, Connecticut; the company's OP980 P.A. amplifier is rated at 120 W and can drive multiple loudspeakers over the wide acoustical, electrical and environmental conditions of the subway car. It will operate in a temperature range of -30 to 80 degrees Celsius, 99 percent humidity and vibration of 2 Gs continuously (8 Gs for as long as 20 minutes). Optim Engineering also designed and builds the audio interface and another small circuit board called the MPL-1. The audio interface contains two audio lines for the passenger voice microphone and the crew voice speaker, replacing the old-fashioned emergency pull cord method. Importantly, the passenger has direct communication with the train driver in the case of an emergency. The MPL-1 contains an electret microphone capsule and provides distortion-free output in extremely loud soundfields of more than 110dB SPL.
The OP980 power amplifier routes the audio to any of four output zones to permit addressing the passenger compartment, the engineer's cabin, and the left or right exterior speakers. Inside the car, the system has eight loudspeakers in a 70V system spaced evenly to provide less than 2dB variation at ear level. Automatic gain adjustment is accomplished based on ambient noise within the car, and a horn-type loudspeaker provides train-side announcements for waiting passengers on the left or right platforms.
“We were contracted to put the audio communications and electronic displays in the new subway car,” said Ed Colford, administrator of subcontractors for Telephonics Corp. “[NYCT] hired Optim Engineering because the design of the products was specific and different than the other products that the company reviewed. In addition to the automatic gain adjustment for the system based on ambient noise, the unique feature is that the loudspeakers are used as microphones to measure the background noise during periods between announcements.”
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