1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 6 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU$!4!G0G0#/-5.)#!4)/.G0G0/6%2G0G04(%G0G04%,%0(/.%.%47/2+-%$)#!,G0G0!.!,/5%G0G0$!4!G0G042!.3-)33)/.-/$%-3)45G134G0G0RecommendationG0G06 (Extract from the “LUEG0“OOK)NOTES1 ITU-T Recommendation V.16 was publishe
2、d in Fascicle VIII.1 of the Blue Book. This file is an extract fromthe Blue Book. While the presentation and layout of the text might be slightly different from the Blue Book version, thecontents of the file are identical to the Blue Book version and copyright conditions remain unchanged (see below)
3、.2 In this Recommendation, the expression “Administration” is used for conciseness to indicate both atelecommunication administration and a recognized operating agency. ITU 1988, 1993All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electroni
4、c ormechanical, including photocopying and microfilm, without permission in writing from the ITU.Fascicle VIII.1 - Rec. V.16 1Recommendation V.16Fascicle VIII.1 - Rec. V.16MEDICAL ANALOGUE DATA TRANSMISSION MODEMS(Geneva, 1976)The CCITT,considering that(a) computer-aided automatic ECG (electro-cardi
5、ogram) interpretation is being made available by specialdiagnostic centres to general practitioners and hospitals at remote places and suitable transmission equipment isnecessary for this reason;(b) such a service can be implemented to advantage in a special data collection system using simple remot
6、estations and a high-quality central unit;(c) for such applications particularly suitable and compatible transmission facilities are necessary whichmust not interfere with other telephone services;(d) analogue as well as digitalized transmission of the analogue data (e.g. ECG records) are in princip
7、lepossible;(e) in most cases, however, on-line transmission with analogue transmission methods can be implementedmore easily and economically;(f) in practice, analogue transmission generally promises a sufficient degree of quality;(g) in cases of emergency and monitoring of implanted pacemakers, ver
8、y simple, acoustically coupledequipment may be of great assistance to the persons concerned;unanimously declares the following view1 Analogue transmission of medical analogue data, e.g. ECGs, should be permitted in the public telephonenetwork. Reliable, sufficiently interference-free transmission ca
9、nnot be taken for granted on every connection or route.Therefore, it is necessary to test the connections under consideration before such a service is definitely introduced.2 This service requires two basically different transmission devices (modems):1) transmission equipment for simultaneous transm
10、ission of three ECG signals on a telephone channel froma remote station to the central station, preferably for direct galvanic coupling to the telephone channel;2) transmission equipment, preferably for emergency use and for monitoring of implanted pacemakers, tosimultaneously transmit only one ECG
11、signal from a remote station to a central station with acoustic orgalvanic coupling to a telephone channel.The ECG station usually consists of an ECG recorder, including separating amplifier, data input/output deviceand the modem specified in this Recommendation (see Figure 1/V.16).The central stati
12、on usually comprises the central modem specified herein and the interpretation system forECGs (e.g. a computer programmed for ECG interpretation).This Recommendation covers the modems, the desired transmission characteristics of the ECG transmissionchannel as well as the necessary interchange circui
13、ts and the method of transmitting the digital data associated with theECG (e.g. patients identification codes, control signals in both transmission directions and the interpretation record).2 Fascicle VIII.1 - Rec. V.163 Modems for simultaneous analogue transmission of three ECG records3.1 Basic cha
14、racteristics of the analogue channelsThe equipment specified below is mainly intended for operation with direct galvanic coupling to telephonelines.3.1.1 Baseband signalBaseband signal requirements at the modem input:- number of simultaneously transmitted ECGrecords 3- frequency response of the sepa
15、rating amplifier flat- signal-to-noise ratio with 10 Hz square wave 50 dBsignals 1 V (unweighted)- full scale limit (see Note 1) 2.5 V- linearity deviation of an ECG channel related tofull scale and the optimum straight line 1%- permissible group delay distortion of the input from 3 to 60 Hzsignal a
16、t the modulator input (including channel 2 ms (outside this range,filter in the baseband) see Figure 2/V.16)Fascicle VIII.1 - Rec. V.16 3- spectrum: if a.c. coupling is applied, a timeconstant of = 3.2 s, corresponding to a lowercut-off frequency of 0.5 Hz, should be used.- baseband pre-emphasis (se
17、e Note 2) (between rise of 6 dB/octave;separating amplifier and modem) cut-off frequency: 15 HzNote 1 - Existing instruments (ECG recorders, etc.) are designed for 2.5 V full scale. If, however, theInternational Electrotechnical Commission specifies 1 V or 1.25 V as the full scale limit, this value
18、should beadopted. The slope of the modulator characteristic (see 3.1.2 below) must then be adjusted accordingly.Note 2 - This value will require further study if, at a later date, amplitude compandors are used to improve thesignal-to-noise ratio.3.1.2 Requirements for the transmission equipment (mod
19、ems)The modem should be capable of transmitting baseband signals with a bandwidth of up to approximately 100Hz. The transmission equipment (modems) should not deteriorate the performance of the baseband signal as specifiedunder 3.1.1 above by more than 10%. The exact value of the admissible deterior
20、ation needs further study.Since the centre channel of the transmission equipment will in future be used for digital transmission of ECG-associated digital data and other biological data, it must be capable of transmitting d.c. components. The same shouldapply to the other channels.- line signals for
21、 transmitting the ECG: signals as specified under 3.1.1 above- modulation method: frequency modulation- subcarrier frequencies fnand associated maximumtransmission levels pn:f1= 950 Hz 6 Hz p1= 7 dB lower than the resultingf2= 1400 Hz 15 Hz (see Note 1) p2= 5 dB level p0as specified inf3= 2100 Hz 15
22、 Hz p3= 3 dB Recommendation V.2- resulting maximum level: p0as specified in Recommendation V.2- simultaneous transmission of all three subcarriersis mandatory, if subcarriers f1and/or f3are used.- maximum frequency deviation per channel in thecase of linear operation: f = 100 Hz4 Fascicle VIII.1 - R
23、ec. V.16- slope of the modulator characteristic (subcarrierdeviation sensitivity): 40 Hz/V (see Note 2)- a positive signal should cause a rise in thesubcarrier frequency- FM channel bandwidth (3 dB points): 350 Hz- resulting level accepted by receiver - 6 dBm to(upper threshold-level): -43 dBm- lowe
24、r threshold level: -46 dBmNote 1 - This frequency selection makes allowance for the following boundary conditions:a) best possible decoupling between the three ECG channels. Nonlinear distortion may cause a small degreeof cross-talk;b) CCITT standardized subcarrier frequencies (2100 Hz and 1400 Hz)
25、should be used as far as possible;c) no interference to existing CCITT signalling systems by simulation of switching signals.Some of the existing ECG transmission systems use subcarrier frequencies f1= 1075 Hz, f2= 1935 Hz,f3 = 2365 Hz. Due to the relatively slow modulation by ECGs, the modulated su
26、bcarrier frequencies f2and f3maysimulate signals of CCITT Signalling Systems No. 2 and No. 4. This would cause interference to the ordinarytelephone service. Where this kind of interference is not to be expected, use of the subcarrier frequencies concernedshould be allowed over a transition period c
27、overing two CCITT study periods. Thereafter, the aforementionedfrequencies (950 Hz, 1400 Hz and 2100 Hz) only should be used in the interest of mutual compatibility of the ECGtransmission systems from different suppliers.Note 2 - This value should be changed to 100 Hz/V, or 80 Hz/V if the full-scale
28、 voltage of 1 V or 1.25 V(see 3.1.1 above) is applied.3.2 Forward digital data transmission from the remote station to the central stationThe analogue centre channel with a subcarrier frequency f2= 1400 Hz should be used for transmission ofECG-associated digital data. Channel characteristics are:- c
29、entre frequency: f2= 1400 Hz (see Note)symbol 1, (mark): fz= f2- 80 Hzsymbol 0, (space): fa= f2+ 80 Hz- coding: International Alphabet No. 5 as indicatedin Recommendations V.3 and V.4, withstart/stop transmission- nominal modulation rate: 100 bauds- power level: p2 -11 dBmNote - In addition to the a
30、forementioned signalling system, the following systems for forward digital datatransmission are also in use:a) tri-level code, derived from frequencies f1,2,3and f1,2,3 approximately 100 Hz;b) serial code with f1= 1075 Hz 40 Hz and frequency shift keying (FSK);c) signalling with push-button telephon
31、e frequencies as specified in Recommendation Q.23 1.These variants should be allowed to remain in use for a transition period of two study periods. Afterwards,only the above recommended version should be used in order to obtain mutual technical compatibility of theinstruments. This should also apply
32、 to future developments.Fascicle VIII.1 - Rec. V.16 53.3 Digital transmission in the backward direction from the central station to the remote stationIn order to send back interpretation results, control signals, etc., a digital backward channel with the followingparameters should be provided:- modu
33、lation by frequency shift keying with the following frequencies:symbol 1 (mark): fz= 390 Hz (see Note)symbol 0 (space): fa= 570 Hz- nominal modulation rate: 200 bauds- coding: International Alphabet No. 5 as indicatedin Recommendations V.3 and V.4, withstart/stop transmission- transmission level: as
34、 specified in Recommendation V.2- idle condition: symbol 1 (mark), 390 Hz- level accepted by receiver: - 6 dBm to -40 dBm- lower threshold level: -46 dBm.Note - fz= 390 Hz is in accordance with Recommendation V.23. For single tone signalling, f = 389 Hz (EIAstandard for tone signalling) should be al
35、lowed for a transition period of two study periods. Afterwards, the aboveCCITT standard should be applied.3.4 Calibration signalAt the beginning of the ECG recording a standardized calibration signal can be transmitted from the ECGrecorder. by transmitting the combination ENQ (0/5) of International
36、Alphabet No. 5 to the remote station (ECGrecorder) the central station should call up and repeat this calibration signal whenever desired.3.5 Quality controlIn order to monitor the transmission quality and eliminate those parts of the transmitted ECG which containinterference pulses, suitable monito
37、ring measures should be provided in the central modem. If a part of the transmittedECG is disturbed, the central unit should send the signal DEL to the remote station.A 40-dB signal-to-noise ratio in the baseband ECG channel is provisionally recommended as threshold level.The exact value needs furth
38、er study.6 Fascicle VIII.1 - Rec. V.163.6 Interchange circuitsThe following interchange circuits should be optional. If interchange circuits are required, the followingcircuits should be provided:3.6.1 Interchange circuits between recording system and remote station modemIf interchange circuits are
39、necessary between the recorder and the modem, their functions should be inaccordance with Recommendation V.24, and their electrical values in accordance with Recommendation V.28 or V.31,except circuits carrying analogue signals.3.6.2 Interchange circuits between the central modem and the interpretat
40、ion systemIf these interchange circuits are necessary, they should also be in accordance with Recommendations V.24 andV.28.The choice of the required interchange circuits needs further study.3.7 ProceduresThe required procedures also need further study with respect to mutual compatibility, echo supp
41、ressordisabling, answering tones, etc.Note - A frequency scheme of subcarrier frequencies and associated digital channels is given in Figure 3/V.16.4 Modem for simultaneous analogue transmission of one ECG record4.1 GeneralThis specification enables single channel equipment for direct galvanic coupl
42、ing or acoustic coupling to bedesigned which is compatible with the centre channel of the three-channel transmission equipment described in 3above.4.2 Baseband signal when transmitting from the remote station to the central unit as specified in 3.1.1 abovebut with the following amendments to be made
43、 to the parameters of the line signals:- frequency: f2= 1400 Hz;- power level: p2 -6 dBm.Fascicle VIII.1 - Rec. V.16 7In the case of acoustic coupling the above power level should not be exceeded at the output of the telephoneset. The full scale limit may be extended to 5 mV. Linear operation is req
44、uired up to 2.5 mV in this case. The slopeof the modulator characteristic should be 40 Hz/mV for linear operation. These parameters are related to the patientscable.4.3 Digital transmission in the forward directionDue to the limited number of possible applications, the use of the digital forward tra
45、nsmission channel shouldbe optional. If provided, it should be in accordance with the digital transmission method described under 3.2 above.4.4 Digital transmission in the backward directionThe use of the digital backward channel should be optional. If provided, it should be in accordance with 3.3ab
46、ove. If no digital backward channel is provided, the answering tone (389 Hz) should be sent.4.5 Single channel central modemIf required, a single channel central modem for direct galvanic coupling to the telephone line can also bedesigned with the parameters of the centre channel. The maximum deviat
47、ion may be extended to 200 Hz. Here, allmeans for transmission of ECG-associated digital data are optional. If provided, they should be in accordance with thedigital transmission method described under 3.2 and 3.3 above.Reference1 CCITT Recommendation Technical features of push-button telephone sets, Vol. VI, Rec. Q.23.
