Large Area Assistive Listening Systems: Review and Recommendations

6. RECEIVERS AND COUPLERS: RECOMMENDATIONS

When hard of hearing people use an ALS, they are not usually concerned with the characteristics of the installation and transmission process of the various systems. They expect, and rightly so, that when they obtain a receiver at some venue that the signal they perceive will be superior to that they could obtain unaided or with their own hearing aids. The nature, characteristics, and operation of ALS receivers proved to be a major concern in all the focus groups. The recommendations given below reflect the comments and suggestions made, but also represent our own best judgements:

• The ALS receiver should be capable of delivering speech at levels of 110 dB SPL, but not to exceed 120 dB SPL.

• Single-channel receivers with only a minimum of external controls should be available for use at locations catering to elderly people (such as nursing homes and senior centers).

• Discrete and highly visible controls should be included in receivers that can detect multiple channels or capable of other electroacoustic modifications (e.g. volume and tone controls).

• All receivers should include "low battery" warning lights, to give adequate battery life warning.

• The output jack of all ALD receivers should accommodate a 1/8" (3.5mm) stereo plug using a TRS (tip, ring, sleeve) configuration, with the sleeve always carrying the ground. In mono systems the signal should be carried on the tip; in stereo systems, on the tip and the ring. This will permit the use of stereo earphones, direct audio input (DAI) cables, neckloops, cochlear implant patch cords, and silhouette inductors.

• Coupling options should include headphones, earbuds, and neckloops. We recommend that one neckloop be available for every four air conduction type receivers.

• Headphones should be able to fit comfortably over in-the-ear hearing aids and permit users to either couple inductively or acoustically. Furthermore, the "bleed" from such receivers should not exceed the ambient noise at a seat adjacent to the user.

6.1 Universal Receiver: Recommendations

The need for a universal receiver was highlighted when it was suggested that standardized transmitting characteristics for both FM and IR ASL be required. This suggestion was not accepted. It was felt that mandating standardized transmitting characteristics to which all the manufacturers would adhere would stifle innovation and creative new developments. Nevertheless, consumers should have the option of purchasing a personal ALS receiver that can be used in any large venue they attend. If "universal access" cannot be obtained by standardizing transmission characteristics, then it should be sought by the development of a "universal" receiver. Such a device was available until quite recently, but is no longer being manufactured. This is an option that should now be resurrected and available to consumers. Many people prefer to purchase their own ALS receiver, one that they could use in any venue with any type of ALS. This is more than just a convenience; it provides these people with the security of knowing that their ALS receiver functions well and in accordance with their personal needs. We have already recommended, above, that venues note the transmitting frequencies of the ALS on their signage.

We recommend that the industry be encouraged to develop a "Universal Receiver", one that can be (1) tuned to any FM frequency used in ALS in the 72‒75 MHz or 216‒127 MHz range, either wide or narrow channel, (2) adjusted to detect any of the sub-carriers used with IR systems, and (3) include a telecoil for usage with IL systems. Additional desirable features would be an environmental microphone and a "low battery" warning light.