Analog Phone Research Articles

Further aspects on cellular and cordless telephones and brain tumours

We included in a case-control study on brain tumours and mobile and cordless telephones 1,617 patients aged 20-80 years of both sexes diagnosed during January 1, 1997 to June 30, 2000. They were alive at the study time and had histopathology verified brain tumour. One matched control to each case was selected from the Swedish Population Register. The study area was the Uppsala-Orebro, Stockholm, Linköping and Göteborg medical regions of Sweden. Exposure was assessed by a questionnaire that was answered by 1,429 (88%) cases and 1,470 (91%) controls. In total use of analogue cellular telephones gave an increased risk with odds ratio (OR)=1.3, 95% confidence interval (CI)=1.04-1.6, whereas digital and cordless phones did not overall increase the risk significantly. Ipsilateral use of analogue phones gave OR=1.7, 95% CI=1.2-2.3, digital phones OR=1.3, 95% CI=1.02-1.8 and cordless phones OR=1.2, 95% CI=0.9-1.6. The risk for ipsilateral use was significantly increased for astrocytoma for all studied phone types, analogue phones OR=1.8,95% CI=1.1-3.2, digital phones OR=1.8, 95% CI=1.1-2.8, cordless phones OR=1.8, 95% CI=1.1-2.9. Use of a telephone on the opposite side of the brain was not associated with a significantly increased risk for brain tumours. Regarding anatomical area of the tumour and exposure to microwaves, the risk was increased for tumours located in the temporal area on the same side of the brain that was used during phone calls, significantly so for analogue cellular telephones OR=2.3, 95% CI=1.2-4.1. For acoustic neurinoma OR=4.4, 95% CI=2.1-9.2 was calculated among analogue cellular telephone users. When duration of use was analysed as a continuous variable in the total material, the risk increased per year for analogue phones with OR=1.04, 95% CI=1.01-1.08. For astrocytoma and ipsilateral use the trend was for analogue phones OR=1.10, 95% CI=1.02-1.19, digital phones OR=1.11, 95% CI=1.01-1.22, and cordless phones OR=1.09, 95% CI=1.01-1.19. There was a tendency of a shorter tumour induction period for ipsilateral exposure to microwaves than for contralateral, which may indicate a tumour promotor effect.

POTS to broadband... Part 1: Anatomy of the telephone system for data communication.

Biomedical Instrumentation & Technology 277 This installment of IT World takes a look at the evolution of POTS (Plain Old Telephone System—and for my regular readers, I did not invent this acronym!) and modems to set the scene for examining newer “broadband” services. As usual the terminology gets a bit blurred in everyday use. This is why I put quotation marks around the broadband term—I’ll show you what I mean later in the column. We’ll talk about data communication on analog phone lines and digital lines along with their expected transfer speeds. In part 2 of this column, in the September-October issue of BI&T, I will focus on ISDN, X.25, Frame Relay mechanisms and protocols. This all leads to a discussion of xDSL, the latest in telephone broadband connections to telephone subscribers. I’m hoping to also cover broadband data communications via CATV cables and systems in part 2 (This is contingent on how wordy I get in part 2. The CATV portion may be delegated to a part 3). In any event, at the end of the discussion, we’ll be able to compare the virtues and disadvantages of each of these broadband techniques.

Screening and follow-up of diabetic retinopathy using a new mosaic 9-field fundus photography system

Aim: To evaluate the clinical usefulness of a newly developed fundus photographing system and assess its applicability to telemedicine. Methods: Nine overlapping 45° fundus photographs were taken by a new camera equipped with nine internal fixation targets to provide standardized 9-field photographs. The digitally stored images were either edited in 3×3 form or reconstructed as collage (9F) and compared to the ophthalmological examination (OP) and single-field non-mydriatic photography (SC). In telemedicine, 9-field images derived from 61 adolescent diabetics were sent to ophthalmologists over an analog phone line. Results: The sensitivities of the examinations by 9F without and with mydriasis (78 and 82%) were equivalent to OP (84%) and superior to SC (64%). The diagnosis of severity by 9F was also comparable to those by OP, whereas SC tended to underestimate the severity. An average of 1 min 19 s was required to send one edited 9-field photography (average size 259±30 KB) over the Internet. Twelve of these eyes were diagnosed as diabetic retinopathy on a desktop monitor whereas SC gave only seven. Conclusion: This new 9-field fundus photography system can be appropriate for the screening and follow-up of diabetic retinopathy in adult and adolescent diabetic subjects, especially when appiled to telemedicine over the Internet.

Mobile phone use and subjective symptoms. Comparison of symptoms experienced by users of analogue and digital mobile phones.

In 1995 many people reported symptoms such as headaches, feelings of discomfort, warmth behind/around or on the ear and difficulties concentrating while using mobile phones. The number of complaints was higher for people using the digital (GSM) system, i.e. with pulse modulated fields, than for those using the analogue (NMT) system. Our main hypothesis was that GSM users experience more symptoms than NMT users. An epidemiological investigation was initiated including 6379 GSM users and 5613 NMT 900 users in Sweden, and 2500 from each category in Norway. The adjusted odds ratio did not indicate any increased risk for symptoms for GSM users compared with NMT 900 users. Our hypothesis was therefore disproved. However, we observed a statistically significant lower risk for sensations of warmth on the ear for GSM users compared with NMT 900 users. The same trend was seen in Norway for sensations of warmth behind/around the ear and in Sweden for headaches and fatigue. Factors distinguishing the two systems (radio frequency emission, phone temperatures and various ergonomic factors) may be responsible for these results, as well as for a secondary finding: a statistically significant association between calling time/number of calls per day and the prevalence of warmth behind/around or on the ear, headaches and fatigue.

A Novel Direct Sequence Spread Spectrum CDMA System with Analog Frequency Modulation

This paper describes and analyzes a unique combination of analog modulation with code division multiple access. Although the capacity of the analog CDMA system is less than that of the digital CDMA, the analog system has reliable voice quality, economy and ease of implementation, simplified frequency planning, and compatibility with current analog phone systems and devices, which is an especially attractive feature. The FM CDMA system is proposed as a fixed wireless system, e.g., wireless local loop, in which the small scale fading distortion due to Doppler effect is likely to be moderate. This allows the use of simple and cost-efficient receiver structures while maintaining performance.

A robust, scalable, object-based video compression technique for very low bit-rate coding

This paper describes an object-based video coding scheme (OBVC) that was proposed by Texas Instruments to the emerging ISO MPEG-4 video compression standardization effort. This technique achieves efficient compression by separating coherently moving objects from stationary background and compactly representing their shape, motion, and the content. In addition to providing improved coding efficiency at very low bit rates, the technique provides the ability to selectively encode, decode, and manipulate individual objects in a video stream. This technique supports all three MPEG-4 functionalities tested in the November 1995 tests, namely, improved coding efficiency, error resilience, and content scalability. This paper also describes the error protection and concealment schemes that enable robust transmission of compressed video over noisy communication channels such as analog phone lines and wireless links. The noise introduced by the communication channel is characterized by both burst errors and random bit errors. Applications of this object-based video coding technology include videoconferencing, video telephony, desktop multimedia, and surveillance video.

Single-chip H.324 videoconferencing

The C82 multimedia-processing DSP helps vendors respond to cost-sensitive consumer and PC markets. As shown here, it implements H.324 videoconferencing over analog phone lines.