1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T P.350 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (03/2001) SERIES P: TELEPHONE TRANSMISSION QUALITY, TELEPHONE INSTALLATIONS, LOCAL LINE NETWORKS Subscribers lines and sets Handset dimensions ITU-T Recommendation P.350 (Formerly CCITT Recommendation)
2、 ITU-T P-SERIES RECOMMENDATIONS TELEPHONE TRANSMISSION QUALITY, TELEPHONE INSTALLATIONS, LOCAL LINE NETWORKS Vocabulary and effects of transmission parameters on customer opinion of transmission quality Series P.10 Subscribers lines and sets Series P.30 P.300 Transmission standards Series P.40 Objec
3、tive measuring apparatus Series P.50 P.500 Objective electro-acoustical measurements Series P.60 Measurements related to speech loudness Series P.70 Methods for objective and subjective assessment of quality Series P.80 P.800 Audiovisual quality in multimedia services Series P.900 For further detail
4、s, please refer to the list of ITU-T Recommendations. ITU-T P.350 (03/2001) i ITU-T Recommendation P.350 Handset dimensions Summary This Recommandation is the follower of Recommandation P.35 (1988). It contains handset dimensions for traditional corded analogue and digital telephones based on head d
5、imension studies. For very short designs information about the influence on the D-factor is given. Source ITU-T Recommendation P.350 was revised by ITU-T Study Group 12 (2001-2004) and approved under the WTSA Resolution 1 procedure on 29 March 2001. Former edition was numbered as CCITT P.35 (1988).
6、ii ITU-T P.350 (03/2001) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating
7、and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce
8、 Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In this R
9、ecommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the
10、 use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendat
11、ion, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. ITU 200
12、1 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from ITU. ITU-T P.350 (03/2001) iii CONTENTS Page 1 Scope. 1 2 Abbreviation . 1 3 Handset dimens
13、ions for analogue and digital telephones. 1 3.1 Traditional handset dimensions 1 3.2 Very short handset designs used for both cordless and mobile applications 2 ITU-T P.350 (03/2001) 1 ITU-T Recommendation P.3501Handset dimensions 1 Scope Handset dimensions for traditional corded analogue and digita
14、l telephones are recommended. For very short designs information about the influence on the D-factor is given. 2 Abbreviation This Recommendation uses the following abbreviation: LSTR Listener Side Tone Rating 3 Handset dimensions for analogue and digital telephones In 3.1 recommendations are given
15、on handset dimensions for analogue and digital telephones based on head dimension studies. These recommendations are applicable for traditional handsets mainly used for corded telephone sets. Very short designs are used for telephone sets for both cordless and mobile applications. In 3.2 the depende
16、ncy of the D-factor and the dimensions is given, based on an investigation. 3.1 Traditional handset dimensions The shape and the dimension of the handset have an important influence on both send and receive levels. The earpiece must be capable of forming a good seal to the ear and the handgrip of th
17、e handset must be such that it will encourage the user to hold it to the head in the optimum position. An ergonomic study was made in the USA in 1931 on the distribution of the relevant finger and head dimensions; 3889 persons were measured, including both male and female subjects. A later head dime
18、nsion study was carried out in the Peoples Republic of China (1977). A subsequent investigation (1978) shows that, for convenience in use, the mouthpiece of the handset should be somewhat outside (e.g. 10-12 mm) a circle enclosing the centre of the lip of 80% of the 4012 subjects tested. A handset c
19、onforming to these dimensions (see Figure 1) will then be acceptable to more than 90% of users. When a longer lip-to-mouthpiece distance is chosen, the signal-to-ambient-noise ratio will be worse, and recommended LSTR values will be more difficult to meet (see ITU-T G.121, P.11, P.76, P.79 and P ser
20、ies Supplement 11). Therefore both signal-to-ambient-noise ratio and mouthpiece position for convenient use must be considered and probably a compromise must be made. Based on the information given above, the ITU-T recommends that handset telephones conform to the dimensions outlined in Figure 1, wi
21、th respect to mouthpiece positions and cheek-to-handset clearance. NOTE An earpiece with a design that forms a good seal to the Type 1 artificial ear (ITU-T P.57) will facilitate testing both in laboratories and during manufacturing. Experience has shown that earpieces with a good seal to the Type 1
22、 artificial ear also give in most cases a good seal to the human ear. _ 1This Recommendation is a revision of CCITT P.35 (1988). 2 ITU-T P.350 (03/2001) T1212970-01136mm30mm14mmQP60 mm22AMouthpieces whose geometryis such that they are tangentto the circle Y in this regionand whose tangent line isgre
23、ater than 30 to the direc-tion of speech, will not onlybe acceptable to more than90% of users but are likelyto improve the signal-to-am-bient noise ratioMinimum recommen-ded clearance forcheek and fingers(conventional handset), d(distance to handsethandle)Directionof speechMinimum recommen-ded cheek
24、 clearance(for wide handsetse.g. those incorpo-rating a dial)Plane tangentto the earcapCircle Y, radius 27 mm, centredon point A (centre of lips)Circle X, radius 15 mm, centred on point A77.1LipplaneFigure 1/P.350 When using the dimensions given in Figure 1 usually a D-factor with a positive value c
25、an be expected. In 1991 it was shown that for handsets of “conventional form“ and with linear microphone circuitry, the D-factor can be estimated by Equation 3-1, using the distance d between the centre of the external opening for the microphone on the surface of the handset and the centre of the li
26、pring of the artificial mouth. However, for designs other than close to “conventional form“, the deviation from the results of the formula can be relatively large. =ddoD lg20 in dB (3-1) Where: do = 45 mm. 3.2 Very short handset designs used for both cordless and mobile applications Cordless and mob
27、ile telephone sets very often do not follow the dimensions given in Figure 1. Short and flat designs are used. In that case, additional attention should be given to the influence of the design on the D-factor. The change of the D-factor, if the microphone positions change along the head up to the mo
28、uth, was studied in 2000 by using a flat design and an omnidirectional microphone. The results are given in Equation 3-2 where l is the distance between the centre of the external opening for the microphone on the surface and the centre of the external opening for the earphone: 32)()()()( lolFzlolFy
29、lolFxDolD += (3-2) Where: lo = 145 mm Do = 5.3 dB ITU-T P.350 (03/2001) 3 Fx = 0.050845mmdBFy = 0.0011152mmdBFz = 0.000000572853mmdBare fixed values. The D-factor can be improved by using a directional microphone. However, the degree of improvement is less than the difference of the microphone free
30、field sensitivities would suggest. There is a strong dependency on how the microphone is mounted in the handset. Geneva, 2001 SERIES OF ITU-T RECOMMENDATIONS Series A Organization of the work of ITU-T Series B Means of expression: definitions, symbols, classification Series C General telecommunicati
31、on statistics Series D General tariff principles Series E Overall network operation, telephone service, service operation and human factors Series F Non-telephone telecommunication services Series G Transmission systems and media, digital systems and networks Series H Audiovisual and multimedia syst
32、ems Series I Integrated services digital network Series J Transmission of television, sound programme and other multimedia signals Series K Protection against interference Series L Construction, installation and protection of cables and other elements of outside plant Series M TMN and network mainte
33、nance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits Series N Maintenance: international sound programme and television transmission circuits Series O Specifications of measuring equipment Series P Telephone transmission quality, telephone installa
34、tions, local line networks Series Q Switching and signalling Series R Telegraph transmission Series S Telegraph services terminal equipment Series T Terminals for telematic services Series U Telegraph switching Series V Data communication over the telephone network Series X Data networks and open system communications Series Y Global information infrastructure and Internet protocol aspects Series Z Languages and general software aspects for telecommunication systems
