1、 TIA DOCUMENT Telecommunications Telephone Terminal Equipment Magnetic Field and Acoustic Gain Requirements for Headset Telephones Intended for Use by the Hard of Hearing TIA-504-A (Revision of TIA/EIA-504) FEBRUARY 1998 TELECOMMUNICATIONS INDUSTRY ASSOCIATION The Telecommunications Industry Associa
2、tion represents the communications sector of NOTICE TIA Engineering Standards and Publications are designed to serve the public interest through eliminating misunderstandings between manufacturers and purchasers, facilitating interchangeability and improvement of products, and assisting the purchase
3、r in selecting and obtaining with minimum delay the proper product for their particular need. The existence of such Publications shall not in any respect preclude any member or non-member of TIA from manufacturing or selling products not conforming to such Publications. Neither shall the existence o
4、f such Documents preclude their voluntary use by non-TIA members, either domestically or internationally. TIA DOCUMENTS TIA Documents contain information deemed to be of technical value to the industry, and are published at the request of the originating Committee without necessarily following the r
5、igorous public review and resolution of comments which is a procedural part of the development of a American National Standard (ANS). Further details of the development process are available in the TIA Engineering Manual, located at http:/www.tiaonline.org/standards/sfg/engineering_manual.cfm TIA Do
6、cuments shall be reviewed on a five year cycle by the formulating Committee and a decision made on whether to reaffirm, revise, withdraw, or proceed to develop an American National Standard on this subject. Suggestions for revision should be directed to: Standards (7) (8) write to CSA Sales Promotio
7、n, Info Update, at the address given above. define the problem, making reference to the specific clause, and, where appropriate, provide an explanation of circumstances surrounding the actual field condition; and be phrased where possible to permit a specific “yes“ or “no“ answer. Interpretations ar
8、e published in CSA s periodical Info Update. For subscrtion details, V STDmEIA TIA-504-A-ENGL 1998 H 3234600 059811112 0113 W TINE IA-504-A Telecommunications - Telephone Terminal Equipment - A coustic and Magnetic Field Requirements for Handset Telephones for Use by the Hard of Hearing i. Scope i .
9、I This Standard defines magnetic field requirements for all handset telephones intended to couple magnetically with hearing aids. , 1.2 This Standard also covers requirements for receive-amplified handset telephones intended for use by the hard of hearing. 1.3 This Standard does not cover other devi
10、ces for the hard of hearing to use the telephone network. 2. Definitions 2. I The following definitions apply in this Standard: Handset telephone - a device equipped with or configured as a handset intended to be held against the ear. Measurement axis - the axis parallel to the reference axis but ma
11、y be displaced from the axis by a maximum of 10 mm (see Figure i). Within this constraint, the measurement axis may be located where the axial and radial field intensity measurements are optimum with regard to the requirements. In a handset with a centred receiver and a circularly symmetrical magnet
12、ic field, the measurement axis and the reference axis would coincide. Measurement plane - the planar area parallel to, and 10 mm in front of, the reference plane (see Figure 1). Receive-amplified handset telephone - a telephone set equipped with a means of increasing the receive outputs, both acoust
13、ic and magnetic, by a specified number of decibels above the normal level. Reference axis - the axis normal to the reference plane and passing through the centre of the receiver cap (or the centre of the hole array, for handset types that do not have receiver caps). Reference plane - the planar area
14、 containing points of the receiver-end of the handset that, 1 STD-EIA TIA-504-A-ENGL 1998 m 3234600 0598113 T5T m TINE IA-504-A in nomal handset use, rest against the ear (see Figure I). ROLR - acronym for Receive Objective Loudness Rating which is defined in IEEE Standard 661. ROLR correlates more
15、closely with human perception of the received loudness of a telephone than does a level measurement at a single frequency. The more positive the ROLR the quieter the receive level. 3. Reference Publications 3.1 Where reference is made to the following Standards such reference shall be considered to
16、refer to that edition listed below: IEEE* Standards Standard Method for Determining the Objective Loudness Ratings of Telephone Conn ec tions; 661-1 979, 1027-1996, Standard Method for Measuring the Magnetic Field Intensity in the Vicinity of a Telephone Receiver. Institute of Electrical and Electro
17、nics Engineers. 4. Technical Requirements - Magnetic Output Requirements for Handset Telephones 4.1 General These criteria shall apply to handset telephones. 4.2 Parameters 4.2.1 Three parameters descriptive of the magnetic field at points in the measurement plane shall be used to ascertain adequacy
18、 for magnetic coupling. These three parameters are axial and radial field intensity at I000 Hz and relative axial field strength vs frequency. 4.2.2 The procedures for determining the parameter values are defined in IEEE Standard 1027. 4.2.3 A test circuit and input signal shall be chosen appropriat
19、e to the type of telephone (eg, analog, digital, proprietary) to be tested. The input signal shall be adjusted to produce an acoustic output of -14 dBPa at 1000 Hz measured in the artificial ear as shown in Figure 2a. 2 STD.EIA TIA-504-A-ENGL 1998 3234b00 0598114 99b W TI NE IA-504-A This same input
20、 signal shall subsequently be used for the magnetic field measurement as shown in Figure 2b. 4.3 Axial Field Strength When measured as specified in Clause 4.2.2, the axial component of the magnetic field directed along the measurement axis and located at the measurement plane shall be greater than -
21、36 dB relative to 1 Alm at 1000 Hz (see Figures I and 2). 4.4 Radial Field Strength When measured as specified in Clause 4.2.2, radial components of the magnetic field as measured at four points 90“ apart, anti at a distance 216 mm from the measurement axis (as selected in Clause 4.3), shall be grea
22、ter than -41 dB relative to 1 Alm, at 1000 Hz (see Figures 1 and 2). 4.5 Axial Magnetic Field Strength vs Frequency Response The frequency response of the magnetic field strength as measured in Clause 4.2.2 shall fall within the acceptable region of Figure 4 over the frequency range of 300-3300 Hz.
23、Note: performance of the U-type receiver used in the 500-type telephone set. The lower limit of the magnetic field intensity vs frequency requirement shown in figure 4 has been tightened some what in the region above I O00 Hz to provide improved performance in ne wer designed products. Although exis
24、ting telephones using the U-type receiver ma y not fit fully within the template shown in Figure 4, this should in no way be interpreted as meaning such telephones do not provide satisfactory magnetic field characteristics for coupling to hearing aids. The magnetic field criteria in this Standard we
25、re originally developed based on the 5. Technical Requirements - Receive-Amplified Handset Telephones 5.1 Acoustic Output Requirements for Receive-Amplified Handset Telephones 5.1.1 With the volume control in the nominal gain position, the handset telephone shall meet the requirements of and be test
26、ed in accordance with the applicable telephone set Standard. The minimum gain setting shall be used for this measurement unless the manufacturer identifies a different setting for the nominal gain level. 5.1.2 With the volume control in the maximum gain position, the Receive Objective Loudness Ratin
27、g (ROLR) shall be a minimum of 12 di3 and a maximum of 18 di3 below the value measured in Clause 5.1.1. Since ROLR is a loudness rating value expressed in dB of loss, lower ROLR values represent louder receive volume levels. The 18 .dB maximum may be exceeded if the receive level is automatically re
28、stored to its nominal value when the telephone is returned to the on-hook state. 3 STDeEIA TIA-504-A-ENGL 1998 3234600 0598115 822 TINE IA-504-A 5.1.3 with the volume control in the maximum gain position and with the input to the handset telephone adjusted to produce a sound pressure level of 16 dBP
29、a in the artificial ear, separate input signals of 500 and I000 Hz shall be used. In each case the total harmonic distortion in the acoustical output shall be less than 10%. 5.2 Magnetic Output Requirements for Receive-Amplified Handset Telephones 5.2.1 With the volume control in the nominal gain po
30、sition, the handset telephone shall meet the requirements and be tested in accordance with Clause 4. The minimum gain setting shall be used for this measurement unless the manufacturer identifies a different setting for the nominal gain level. 5.2.2 With the volume control in the maximum gain positi
31、on, the axial and radial magnetic field strengths shall be a minimum of 12 dB and a maximum of 18 dB above the values measured in Clause 5.2.1. The 18 dB maximum may be exceeded if the axial and radial magnetic field strengths level is automatically restored to its nominal value when the telephone i
32、s returned to the off-hook state. The axial field frequency response characteristics shall continue to fall within the relative response template of Figure 4. 5.2.3 With the volume control in the maximum gain position and with the input to the handset telephone adjusted to produce an acoustic output
33、 with a pressure level of 16 dBPa in the artificial ear, separate input signals of 500 and I000 Hz shall be used. In each case the total harmonic distortion in the magnetic output shall be less than 10%. 6. Marking 6.1 In addition to markings required by other Standards, it is recommended that hands
34、et telephones that meet all requirements of this Standard bear the International Symbol of Access-Hearing Impairment (see Figure 5). 4 Ti NE I A-504-A Radial Component / LReference Axis S16 mm 4 _- -?- h Component Measurement O “2 ir Reerence Plane Plane t Measurement Axis Figure 1 Reference and Mea
35、surement Planes and Axis (See Clauses 2.1, 4.3, and 4.4.) 5 STD-EIA TIA-504-A-ENGL 3778 m 3234b00 0578337 bT5 m TINE IA-504-A I- 1 integraort .15 nF B.W. = 100 Hr L -I Feed Circuit Feed Tel. Level Circ. Set Recorder I ?Select /or suitable collector current tSee IEEE Standard 7027. Section 4.2. $See
36、Figure 3. (Integraior shall be calibrated with the probe coil.) Figure 2 Measurement Block Diagram (See Clauses 4.2.3, 4.3, and 4.4.) 6 6.5 mm Max. 1 TINEIA-504-A 2.3 mm Max. Diameter Typical Parameters of Probe Coil DC resistance:900 R inductance:l50 mH Sens i tivi ty:-60 d BV/(A/m) For calibration
37、 see IEEE Standard 1027, Section 5. Figure 3 Probe Coil (Magnetic Material Core) Parameters (See Figure 2.) 7 STD-EIA TIA-504-A-ENGL 1998 W 3234b00 0598339 478 W TINE IA-504-A 21 11 ! C -6.4 -10 -20 I i I Unacceptable Region I -2 dB i / I I . I I I I I I I I I Una 1 I I Regov, -9 icceptable Inn I I
38、I I I I I O O O O O O O o cv o O O v 0 Frequency (Hz) +2 -1 7.6 Figure 4 Relative Axial Magnetic Field Intensity vs Frequency (See Clauses 4.5 and 5.2.2.) . STD-EIA TIA-504-A-ENGL 1998 m 3234600 0598320 19T m TINEIA-504-A Figure 5 Internationally Agreed Symbol to Indicate Availability of Facilities
39、for the Hard of Hearing (See Clause 6.1 .) 9 TINEIA-504-A Annex A Differences between TJA/EiA-504-A- 1996and EJA-504- 1988 and CANICSA T5 15-97 and CSA CAN3-T5 15-M85 regardhg the Measurement of Magnetic Output Note: This Annex is not a mandatory part of this Standard and is included for information
40、 purposes only. Al. General Although both the field strength limits and the magnetic Field Strength-versus-Frequency tolerance mask appear different than in EIA 504-1988 and CSA CAN3-T515-M85, there has been no change in actual requirements as is explained below. FCC Part 68.316-1993 uses the method
41、ology described in EIA-504-1983. IEEE Standard 1027-1996 is a good source of information on test methods. A2. Magnetic Field Strength The test level used in this Standard is nominally 14 dB less than that used in previous editions; therefore the measured field is reduced correspondingly. signal from
42、 a 900 ohm source to the feed circuit of the telephone. The magnetic field strength was then measured with the probe coil. This input level produces a nominal sound pressure of 94 dB SPL when the handset is sealed to an IEC 318 artificial ear. This Standard requires that the input signal be adjusted
43、 until 80 dB SPL is produced in the artificial ear. This test level is then used for field strength tests. Since the nominal input level with the new procedure is 14 dB less than that used previously, the corresponding axial and radial magnetic field strength limits have been reduced by 14 dB also.
44、Table Al illustrates this change. Previously the magnetic field strength was measured by applying a -10 dBV, 1000 Hz Table AI Test Level Difference between previous editions and this Standard Parameter TlA/EIA404-1988 CSA T515-M85 Current Revision Sound pressure in the Artificial Ear Axial Field Int
45、ensity Radial Field intensity 94 dB SPL Nominal ) -22 dB Nm ) -27 dB Nm 80 dB SPL ) -36 dB Aim )41 dBAim A3. Magnetic Field Strength vs Frequency The sensitivity of the probe coil used to measure the magnetic field of the handset increases at rate of 6 dB per octave with increasing frequency. in ord
46、er to obtain the true magnetic strength of the handset receiver at different frequencies, this rising sensitivity must be accounted for. 10 TINE I A-504-A Table A2 Example Correction Factors Frequency (Hz) Correction (dB Am) 1 O0 20.0 125 18.1 180 200 250 300 315 400 500 630 800 I O00 1250 15.9 14.0
47、 12.0 10.5 10.0 8.0 6.0 4.0 1.9 0.0 -1.9 1600 -4.1 2000 -6.0 2500 -8.0 31 50 -10.0 3300 -1 0.4 4000 -12.0 5000 -14.0 6300 -16.0 8000 1 O000 -18.1 -20.0 Rather than applying correction to measured data, the previous Standard incorporated a 6 dB per octave clope into the tolerance mask. (Figure AI sho
48、ws this tolerance mask and is 11 STD-EIA TIA-504-A-ENGL 3998 3234600 0598323 9T9 TINE IA-504-A the one referred to in FCC Part 68.316 for receivers with an axial field strength that exceeds -22 dB Alm.) This revised Standard requires that the measured data be corrected by the integration of the prob
49、e output voltage by either using an electrical integrator or by computational methods. Since the 6 dB per octave slope is removed from the measurement data, the tolerance mask is adjusted likewise. Table A2 gives the correction that must be applied to the measured output of the probe at various frequencies. It is assumed that the coil is calibrated at 1000 Hz. Refer to IEEE 1027 for the calculation of the correction required at other frequencies. 20 I I I 10 Probe Coil Voltage relative to 1000 Hz (dB) o -1 o I I I I 300 5
