1. If the ambient electromagnetic noise (generally caused by lighting regulation systems or major power supplies) produces a field strength exceeding 30mA/meter at frequencies that would decrease the signal-to-noise ratio specified in Item 4, then it is recommended that, unless the noise can be reduced, an induction loop system not be considered.
2. If the eletromagnetic signal produced by a nearby induction loop system spills over into a new user area being considered for a different induction loop system and produces an average magnetetic field strength exceeding 15 mA/meter, then it is recommended that, unless the use of each system can be scheduled so as not to occur simultaneously, an induction loop system not be considered in the new area.
3. Given an input signal to the amplifier that has a constant level over a minimum frequency range of 100 Hz to 8,000 Hz, the measured frequency response of the magnetic field generated by the induction loop system over that range shall not vary by more than +/-3 decibels from the value of 1,000 Hz. In actual usage, graphic equalization of the output signal is allowed.
4. Given an output power level equal to the average value specified in Item 6, the minimum signal-to-noise ratio of the program signal carried by the electromagnetic field shall be at least 30 decibels.
5. Given a 1,000 Hz input signal to the amplifier that has a level sufficient to produce the minimum signal-to-noise ratio specified in Item 4, the harmonic distortion between the input signal and the program signal carried by the electromagnetic field shall not vary by more than 5 percent over the field strength range specified in Item 6.
6. Given a 1,000 Hz sinusoidal input signal, at a level equal to the long-time average level of a speech signal, the average value of the magnetic field strength generated within the user area by the loop shall equal 100mA/meter +/-3 decibels.
The maximum value of the magnetic field strength for a system set to the above recommended average value shall be 400 mA/meter (derived on the basis that the difference of the maximum short-time average level between a speech signal - approximately 0.125 seconds and the long-time average level is approximately 12 decibels).
Both measurements shall be made 48 inches (1219 mm) above floor level at any point within the user area.
The maximum value of the magnetic field strength for a system set to the above recommended average value shall be 400 mA/meter (derived on the basis that the difference of the maximum short-time average level between a speech signal - approximately 0.125 seconds and the long-time average level is approximately 12 decibels).
Both measurements shall be made 48 inches (1219 mm) above floor level at any point within the user area.
7. If a hand-held receiver with[in] earphone is used, the specifications in Items 3, 4 and 5 shall apply. Additionally, the sound pressure level generated by the receiver and earphone shall be at least 80 decibels.
The maximum high-frequency average sound pressure level generated by the receiver earphone shall not exceed 130 decibels.
The maximum high-frequency average sound pressure level generated by the receiver earphone shall not exceed 130 decibels.
8. The system must have inputs capable of accepting signals at line level and microphone level and must be capable of interfacing with existing public address systems or stand alone.
9. Any stand-alone devices powered by 110-120 volt AC used as part of the system must have been tested by an approved laboratory.
10. All input and output wiring must comply with NFPA 70. Output wiring may be enclosed in nonmetallic raceways or molding.
11. The installation of all stand-alone components of the system must comply with all state and local codes.