TCM-40DV

SERVICE MANUAL

Ver 1.0 1999. 04

US Model Canadian Model AEP Model E Model
Model Name Using Similar Mechanism Tape Transport Mechanism Type

TCM-36 MT-40-118

SPECIFICATIONS

CASSETTE-CORDER

MICROFILM
SECTION 1 SERVICING NOTES
TABLE OF CONTENTS 1. 2. 3. 4. 5. 6. SERVICING NOTES.. 2 GENERAL.. 3 DISASSEMBLY.. 4 MECHANICAL ADJUSTMENTS.. 6 ELECTRICAL ADJUSTMENTS.. 7 DIAGRAMS
In this set, the S102 (POWER) detects REC/PLAYBACK on. It is mounted on the MAIN board, and therefore the REC/PLAYBACK on cannot be detected with the MAIN board removed. When making an operation check and voltage check of mechanical deck with the MAIN board removed, fix the S102 at turn on. MAIN BOARD (Conductor Side)
6-1. Block Diagram... 8 6-2. Printed Wiring Boards.. 10 6-3. Schematic Diagram.. 13
EXPLODED VIEWS.. 19 ELECTRICAL PARTS LIST. 22

S102 on

Flexible Circuit Board Repairing Keep the temperature of the soldering iron around 270 C during repairing. Do not touch the soldering iron on the same conductor of the circuit board (within 3 times). Be careful not to apply force on the conductor when soldering or unsoldering. Notes on chip component replacement Never reuse a disconnected chip component. Notice that the minus side of a tantalum capacitor may be damaged by heat.

SECTION 2 GENERAL

Location of Controls
This section is extracted from instruction manual.

TAPE COUNTER VOL EAR

Flat mic Micropohone plat REC TIME
rREC pSTOP 9PLAY SPEED CONTROL 0REW/REVIEW )FF/CUE

VOR BATT/REC/i

PAUSEc

DC IN 3 V

SECTION 3 DISASSEMBLY
This set can be disassembled in the order shown below.
Cabinet (Rear), Cassette Lid
MAIN Board, Mechanism Deck (MT-40-118)
Note: Follow the disassembly procedure in the numerical order given.
CABINET (REAR), CASSETTE LID

8 cassette lid

7 boss
9 cassette spring 3 claw 6 flexible board (CN102) 7 boss

3 claw

5 strap
4 cabinet (rear) 2 screw 3 two claws 1 three screws (B1.7 10)
MAIN BOARD, MECHANISM DECK (MT-40-118)
Note: On installation MAIN board adjust the S105 and button (pause).
6 three screws (IB lock) 7 claw

button (pause)

8 mechanism deck (MT-40-118)
1 Remove four solders of motor leads (M901).
5 MAIN board 2 Remove the two solders 4 screw of the head lead (HRP901). (M1.4) 3 screw (1.7)

NOTE FOR INSTALLATION

MAIN BOARD On installation MAIN board adjust the S101 and REC lever.

screw (1.7)

screw (M1.4)

MAIN board

REC lever
SECTION 4 MECHANICAL ADJUSTMENTS

1 capstan belt

2 FR belt

3 counter belt

1. Clean the following parts with a denatured-alcohol-moistened swab: record/playback head pinch roller erase head rubber belt capstan 2. Demagnetize the record/playback head with a head demagnetizer. (Do not bring the head demagnetizer close to the erase head.) 3. Do not use a magnetized screwdriver for the adjustments. 4. After the adjustments, apply suitable locking compound to the parts adjusted. 5. The adjustments should be performed with the rated power supply voltage (2.5 V) unless otherwise noted. Torque Measurement
Mode FWD Forward Back Tension FF, REW CQ-102C Torque Meter Meter Reading gcm (0.31 0.67 ozinch) 1.0 4.5 gcm (0.014 0.063 ozinch) more than 50 gcm (more than 0.69 ozinch)

CQ-201B

Tape Tension Measurement
Mode FWD Tension Meter CQ-403A Meter Reading more than 50 g (more than 1.76 oz)

FR belt capstan belt

pulley (FR) assy pulley counter

counter tape

counter belt motor DC flywheel assy
SECTION 5 ELECTRICAL ADJUSTMENTS
Setting: Supplied voltage: 2.5 V Switch and control position VOL contorl (RV401) : mechanical center PAUSE switch (S105) : OFF SPEED CONTROL (RV605): center click VOR switch (S104) : OFF Test Tape
Type P-4-A063 WS-48A Signal 6.3 kHz, 10 dB 3 kHz, 0 dB Used for head azimuth adjustment tape speed adjustment

SECTION 6 DIAGRAMS

6-1. BLOCK DIAGRAM

MIC101 (MIC)

Tape Speed Adjustment Mode: playback
test tape WS-48A (3 kHz, 0 dB) 32 set

frequency counter

SIGNAL PATH : PLAY : RECORD

VREF Q101 AGC CONTROL

MIC (PLUG IN POWER)

EAR jack (J101)

MIC AMP, REC/PB EQ AMP IC101 (1/2)
0 dB=0.775 V Record/Playback Head Azimuth Adjustment Mode: playback
test tape P-4-A063 (6.3 kHz, 10 dB) 32 set

REC HRP901 (REC/PB)

S101 (4/6) 29
Specification values: 3,030 to 3,050 Hz 3. Set [RECTIME] switch (S601) to DOUBLE (2.4 cm/s) position. 4. Playback the tape from the beginning for two minutes, then adjust RV606 so that frequency counter reading becomes 1,540 Hz. Specification values: 1,535 to 1,545 Hz Confirm that deflection of the frequency counter reading between the beginning and the end of tape is within 0.5% (NORMAL: approx. 15.2 Hz, DOUBLE: approx. 7.6 Hz). Adjustment Location: MAIN BOARD (Conductor Side)

EQ AMP PRE NF

NF J101 VOR LOW SWITCH Q402 VOR ON SWITCH Q403 VOR DELAY EAR VOX Q502 MUTE SWITCH VOICE MIRROR Q503 OFF Q401 VOR OFF SWITCH LED DRIVE PB B+ Q106 REC/PB MONITOR LEVEL SWITCHING POWER ON B+

level meter

VREF HE901 (ERASE) S101 (1/6)

ALC CONT

Procedure: 1. Turn the adjustment screw to obtain the maximum reading on level meter.
Note: Several peaks may appear, but take the maximum.
Q103 REC EQ SWITCH REC AMP REC IN 3

REC OUT

2. After the adjustment, lock the adjustment screw with suitable locking compound. Adjustment Location:

RV605 SPEED CONTROL

S101 (6/6) (REC/PB) PB REC

TH602 S101 (6/6)

adjustment screw
COMPARATOR IN+ 13 OUT + 15 VSP 14 SPEED CONTROL M901 (CAPSTAN/REEL) UOUT 20 VOUT 1 WOUT 2
12 VREF SWITCH & LOGIC CIRCUIT OSC CIRCUIT BIAS REFERENCE VOLTAGE S/S

MOTOR DRIVE CIRCUIT

Press the ( button.
RV606 Tape Speed Adjustment (Double Speed)
V CAPSTAN/REEL MOTOR DRIVE IC601 7
MOTOR BRAKE SWITCH Q603, 604 VREF MOTOR BRAKE CONTROL SWITCH Q601, 602
RV604 Tape Speed Adjustment (Normal Speed)
Procedure: 1. Set [RECTIME] switch (S601) to NORMAL (4.8 cm/s) position, and playback the tape (WS-48A). 2. Adjust RV604 so that frequency counter reading becomes 3,040 Hz.
Q104 PB EQ SWITCH PRE OUT

REC B+ RV101 VOL

S101 (2/6) (REC/PB) PB REC
POWER AMP, VOR CONTROL, REGULATOR, CAPSTAN/REEL MOTOR DRIVE IC101 (2/2)

S101 (3/6) (REC/PB) PB REC

S101 (REC/PB) PB

MIC IN

MIC AMP

BUFFER Q102
POW OUT POW IN POWER AMP 12 POW OUT 2 14

SP901 (SPEAKER)

REC B+

REC B+ H

S401 VOR L
24 D503 BATT PB B+ Q404 SWITCHING D502 BATT /REC

R/P SW

PAUSE PAUSE

S105 PAUSE c OFF

22 D603

REC/PB

THP606
S601 REC TIME DOUBLE NORMAL RV604, 606 TAPE SPEED 16 GVN OUT MOTOR DRIVER MOTOR CONTROL SWITCH Q605

MUTE SWITCH Q109, 110

POWER ON B+

GVN VREF GVN CONT

VCC 18

BATTERY B+ PB B+

S101 (5/6) (REC/PB) 26 REC B+ PB REC 27

MIC VCC

POWER ON B+ REGULATOR RIPPLE FILTER VCC 15 S102 (POWER)
DRY BATTERY SIZE AA (IEC DESIGNATION R6) 2PCS. 3V CN101 DC IN 3V
VREF REFERENCE VOLTAGE GENERATOR

BATTERY B+

REFERENCE VOLTAGE MUTE SWITCH Q107, 108
VOLTAGE DETECT IC501 VCC BOOSTER CIRCUIT COMPARATOR VS

D501 i

LED DRIVE Q501

SCHEMATIC DIAGRAM

See page 17 for IC Block Diagrams.
Note on Schematic Diagram: All capacitors are in F unless otherwise noted. pF: F 50 WV or less are not indicated except for electrolytics and tantalums. All resistors are in and 1/4 W or less unless otherwise specified. C : panel designation. U : B+ Line. H : adjustment for repair. Total current is measured with no cassette installed. Power voltage is dc 3 V and fed with regulated dc power supply from external power voltage jack. Voltages and waveforms are dc with respect to ground under no-signal conditions. no mark : PLAY < > :RECORD Voltages are taken with a VOM (Input impedance 10 M). Voltage variations may be noted due to normal production tolerances. Signal path. E : PLAY a : RECORD
MECHANISM DECK SECTION-2 (MT-40-118)

111 116

not supplied

129 131

Ref. No. 117 Part No. 3-321-483-11 3-701-437-51 X-3372-171-1 3-924-623-01 3-924-621-01 3-924-620-01 X-3370-388-1 3-924-642-01 3-924-629-01 3-925-207-01 3-924-630-01 X-3370-387-1 3-924-682-01 X-3370-385-1 3-924-628-01 Description RING, RETAINING (0.25) WASHER FLYWHEEL ASSY LEVER (PLAY) LEVER (REW) LEVER (FF) TABLE ASSY, FELT SPRING (FR), TORSION LEVER (DETECTION) SPRING (SHUT. OFF), TENSION LEVER (S. OFF) LEVER ASSY, IDLER BELT (FR) PULLEY (FR) ASSY LEVER (FR) Remark Ref. No. HE901 Part No. 3-035-368-01 3-924-684-01 3-924-619-01 3-924-639-01 3-924-618-01 3-925-208-01 3-924-624-01 X-3377-249-3 3-924-613-01 3-024-378-21 3-703-925-21 3-936-405-01 3-578-242-11 3-014-082-01 3-321-483-31 Description SPRING (PR2), TORSION SPRING (LOCK PLATE), TENSION LEVER (SW) LEVER (CR) LEVER (LOCK) SPRING (REC), TENSION LEVER (REC) CHASSIS SUB ASSY GEAR (FR) SPRING (FR LEVER), TORSION SCREW (M1.4) LEVER (RELEASE) WASHER SPACER RING, RETAINING Remark

128 125

3-924-633-01 SPRING (STOP), TENSION 3-924-622-01 LEVER (STOP)
3-704-197-91 SCREW (IB LOCK) 1-500-515-11 HEAD, MAGNETIC (ERASE)
SECTION 8 ELECTRICAL PARTS LIST
Items marked * are not stocked since they are seldom required for routine service. Some delay should be anticipated when ordering these items. SEMICONDUCTORS In each case, u: , for example: uA. : A. uPA. : PA. uPB. : PB. uPC. : PC. uPD. : PD. CAPACITORS uF: F COILS uH: H When indicating parts by reference number, please include the board.
NOTE: Due to standardization, replacements in the parts list may be different from the parts specified in the diagrams or the components used on the set. -XX and -X mean standardized parts, so they may have some difference from the original one. RESISTORS All resistors are in ohms. METAL: Metal-film resistor. METAL OXIDE: Metal oxide-film resistor. F: nonflammable

Ref. No.

Part No.

Description

Remark
Ref. No. C127 C128 C129 C130 C132 C134 C136 C137 C138 C140 C141 C142 C145 C146 C401 C402 C403 C404 C501 C502 C503 C504 C505 C601 C602 C603 C604 C605 C606 C607 C608 C609 C610 C611
Description 220uF 100uF 22uF 0.047uF 1uF 0.0033uF 1uF 1uF 1uF 0.001uF 0.001uF 0.001uF 0.001uF 0.001uF 22uF 2.2uF 2.2uF 4.7uF 0.1uF 10uF 1uF 0.0022uF 10uF 2.2uF 0.068uF 0.068uF 0.068uF 0.047uF 0.22uF 2.2uF 0.47uF 20% 20% 20% 50V 10%
Remark 4V 4V 6.3V 16V 50V 16V 16V 16V 50V 50V 50V 50V 50V 6.3V 50V 16V 4V 25V 4V 16V 100V 16V 16V 25V 25V 25V 25V 16V 16V 16V 50V 4V 16V
A-3021-225-A LED BOARD, COMPLETE ******************** 1-672-147-11 CONNECTION FLEXIBLE BOARD < DIODE > D501 D502 D503 8-719-057-99 LED SML-211YT-T86 (i) 8-719-059-96 LED SML-210LT-T86 (BATT r, REC) 8-719-059-96 LED SML-210LT-T86 (BATT rr) < SWITCH > S401 1-692-605-31 SWITCH, SLIDE (VOR) S601 1-571-277-51 SWITCH, SLIDE (REC TIME) ************************************************************** * A-3021-227-A MAIN BOARD, COMPLETE ********************* 3-008-612-01 TERMINAL, PLUS < CAPACITOR > C101 C102 C103 C104 C105 C106 C107 C108 C109 C110 C111 C112 C113 C114 C115 C116 C117 C118 C119 C120 C121 C124 C125 C126 1-164-004-11 1-164-161-11 1-107-682-11 1-135-151-21 1-135-151-21 1-163-009-11 1-163-077-00 1-163-017-00 1-163-001-11 1-109-982-11 1-135-151-21 1-164-182-11 1-164-005-11 1-164-346-11 1-164-161-11 1-164-346-11 1-163-009-11 1-164-489-11 1-164-489-11 1-126-153-11 1-163-205-00 1-124-259-11 1-124-434-00 1-164-346-11 CERAMIC CHIP CERAMIC CHIP CERAMIC CHIP TANTALUM CHIP TANTALUM CHIP CERAMIC CHIP CERAMIC CHIP CERAMIC CHIP CERAMIC CHIP CERAMIC CHIP TANTALUM CHIP CERAMIC CHIP CERAMIC CHIP CERAMIC CHIP CERAMIC CHIP CERAMIC CHIP CERAMIC CHIP CERAMIC CHIP CERAMIC CHIP ELECT CERAMIC CHIP ELECT ELECT CERAMIC CHIP 0.1uF 0.0022uF 1uF 4.7uF 4.7uF 0.001uF 0.1uF 0.0047uF 220PF 1uF 10% 10% 10% 20% 20% 10% 10% 5% 10% 10% 25V 100V 16V 4V 4V 50V 25V 50V 50V 10V 4V 50V 25V 16V 100V 16V 50V 16V 16V 6.3V 50V 16V 4V 16V

8-729-420-24 TRANSISTOR 2SB1218A-QRS < RESISTOR >
R101 R102 R103 R104 R105 R106 R108 R109 R110 R111
1-216-065-00 1-216-049-11 1-216-069-00 1-216-073-00 1-216-061-00 1-216-061-00 1-216-085-00 1-216-037-00 1-216-037-00 1-216-075-00
RES, CHIP RES, CHIP METAL CHIP METAL CHIP METAL CHIP METAL CHIP METAL CHIP METAL CHIP METAL CHIP METAL CHIP
4.7K 1K 6.8K 10K 3.3K 3.3K 33K 12K
5% 5% 5% 5% 5% 5% 5% 5% 5% 5%
1/10W 1/10W 1/10W 1/10W 1/10W 1/10W 1/10W 1/10W 1/10W 1/10W
1-216-069-00 METAL CHIP 1-216-069-00 METAL CHIP 1-216-061-00 METAL CHIP
< VARIABLE RESISTOR > RV101 RV604 RV605 1-225-597-11 RES, VAR, CARBON 10K (VOL) 1-238-663-11 RES, ADJ, CARBON 4.7K 1-225-293-11 RES, VAR, CARBON 10K (SPEED CONTROL)

TCM-40DV MAIN

Ref. No. RV606 Part No. Description Remark Ref. No. Part No. Description Remark 1-238-663-11 RES, ADJ, CARBON 4.7K < SWITCH > S101 S102 S105 1-771-321-11 SWITCH, SLIDE (REC/PB) 1-771-092-21 SWITCH, PUSH (1 KEY) (POWER) 1-572-922-11 SWITCH, SLIDE (PAUSE c) < THERMISTOR > TH602 1-809-350-21 THERMISTOR, NTC (2125) THP606 1-810-794-11 THERMISTOR, POSITIVE ************************************************************ MISCELLANEOUS ************** HE901 HRP901 M901 1-548-582-11 1-649-600-11 1-500-515-11 1-500-073-51 1-698-875-11 COUNTER, TAPE (SMALL TYPE) MOTOR FLEXIBLE BOARD HEAD, MAGNETIC (ERASE) HEAD, MAGNETIC (RECORD/PLAYBACK) MOTOR, DC (CAPSTAN/REEL) (WITH PULLEY)
SP901 1-505-838-11 SPEAKER (3.6cm) ************************************************************ ACCESSORIES & PACKING MATERIALS ******************************* 3-864-568-11 MANUAL, INSTRUCTION (ENGLISH, FRENCH) (US, Canadian) 3-864-568-21 MANUAL, INSTRUCTION (ENGLISH, SPANISH, PORTUGUESE) (AEP, E) 3-864-568-31 MANUAL, INSTRUCTION (FRENCH, GERMAN, DUTCH) (AEP) 3-864-568-41 MANUAL, INSTRUCTION (SWEDISH, ITALIAN, FINNISH) (AEP) 3-864-568-51 MANUAL, INSTRUCTION (CHINESE, ENGLISH) (Chinese) 3-864-568-61 MANUAL, INSTRUCTION (CHINESE) (E) 3-864-568-71 MANUAL, INSTRUCTION (SPANISH) (US)

Sony Corporation

9-926-970-11
Personal A&V Products Company
99D0584-1 Printed in Japan 1999. 4 Published by Quality Engineering Dept. (Shinagawa)

Original article

Electromagnetic fields produced by incubators influence heart rate variability in newborns
C V Bellieni,1 M Acampa,2 M Maffei,1 S Maffei,2 S Perrone,1 I Pinto,3 N Stacchini,3 G Buonocore1
Department of Paediatrics, Obstetrics and Reproductive Medicine, University of Siena, Italy; 2 Department of Clinical Medicine and Immunological Sciences, Section of Internal Medicine, University of Siena, Italy; 3 Department of Environmental Physics, Unita ` sanitaria Locale 7, Siena. Italy Correspondence to: Dr C V Bellieni, Policlinico Le Scote, Viale Mario Bracci, Siena, 53100 Italy; bellieni@iol.it Accepted 14 February 2008 Published Online First
ABSTRACT Background: Incubators are largely used to preserve preterm and sick babies from postnatal stressors, but their motors produce high electromagnetic fields (EMFs). Newborns are chronically exposed to these EMFs, but no studies about their effects on the fragile developing neonatal structure exist. Aim: To verify whether the exposure to incubator motor electric power may alter autonomous nervous system activity in newborns. Material and methods: Heart rate variability (HRV) of 43 newborns in incubators was studied. The study group comprised 27 newborns whose HRV was studied throughout three 5-minute periods: with incubator motor on, off, and on again, respectively. Mean HRV values obtained during each period were compared. The control group comprised 16 newborns with constantly unrecordable EMF and exposed to changes in background noise, similar to those provoked by the incubator motor. Results: Mean (SD) total power and the high-frequency (HF) component of HRV increased significantly (from 87.1 (76.2) ms2 to 183.6 (168.5) ms2) and the mean lowfrequency (LF)/HF ratio decreased significantly (from 2.0 (0.5) to 1.5 (0.6)) when the incubator motor was turned off. Basal values (HF = 107.1 (118.1) ms2 and LF/ HF = 1.9 (0.6)) were restored when incubators were turned on again. The LF spectral component of HRV showed a statistically significant change only in the second phase of the experiment. Changes in background noise did not provoke any significant change in HRV. Conclusion: EMFs produced by incubators influence newborns HRV, showing an influence on their autonomous nervous system. More research is needed to assess possible long-term consequences, since premature newborns may be exposed to these high EMFs for months.
One of the main concerns about people in contact with electric devices is their exposure to electromagnetic fields (EMFs). Concern arose when evidence was given that EMFs can alter some neurological or clinical measures in the population: for instance, research disclosed that EMFs produced by cell phones could alter EEG brain activity in humans,1 and several epidemiological studies have found an association between exposure to EMFs and health effects, including childhood leukaemia and adult brain cancer. Experts strongly disagree about whether this association is causal and, if so, how strong it is2; however, in 2001, an expert group of the International Agency for Research on Cancer (an institution belonging to the WHO) reviewed reports on the carcinogenicity of EMFs. Weighting the evidence from cellular, animal and human studies (especially
Arch Dis Child Fetal Neonatal Ed. doi:10.1136/adc.2007.132738
from epidemiological studies on childhood leukaemia), they classified these fields as possibly carcinogenic to humans.3 Additionally, recent research has concluded that occupational exposure to a 50 Hz EMF could influence the neurovegetative regulation of the cardiovascular system,and studies suggest a precautionary attitude toward the exposure of infants to EMFs.6 Despite of this, newborns and especially premature babies may have to be kept for months in neonatal incubators, at an age when developing tissues may be more susceptible to environmental influences; and in incubators they are exposed continuously to a high level EMF produced by an electric motor which is close to babys body, and whose function is to warm and circulate the air which surrounds the baby. In a previous paper we reported EMF levels in common neonatal incubators, finding levels of magnetic flux density well over 10 mG at mattress level.7 These values were similar to those found in two previous studies on EMFs in infant incubators,though higher than values recorded in two other reports.Nevertheless, as far as we know, no studies of the effects of an incubator-generated EMF on the newborns autonomic nervous system (ANS) have ever been performed, though development of the ANS has been correlated with the risk of developing arrhythmias12 and sudden infant death syndrome.Our study aimed to assess whether EMFs to which newborns are exposed in incubators influence physiological variables. We concentred on heart rate variability (HRV), since it is easy to assess and it has been shown to be altered by an EMF in adults: occupational exposure to EMF may be a risk factor for life-threatening cardiac arrhythmias and myocardial infarction15 16; Tabor et al found that an EMF of 200300 mG affected HRV,17 and Sastre et al showed that nocturnal exposure to intermittent 200 mG magnetic fields significantly reduced HRV.18 Bortkiewicz et al subsequently showed that occupational exposure to an EMF of 200300 mG increased the risk of a decrease in HRV and sympathetic dominance, both risk factors for cardiac arrhythmias.19 HRV represents variations in instantaneous heart rate and is considered to be a marker of cardiac ANS activity. Spectral analysis shows various frequency components of HRV: the lowfrequency (0.040.15 Hz) component (LF) is modulated by both the sympathetic nervous system and the parasympathetic nervous system, and the high-frequency (0.150.4 Hz) component (HF) is mainly modulated by the parasympathetic

nervous system. The LF/HF ratio in HRV is used to assess a predominant shift in the sympatho-parasympathetic balance,20 which has been hypothesised to be correlated with sudden infant death.21 We want to assess whether EMFs produced by incubators alter newborns sympatho-vagal balance. of the fan background noise.22 To reproduce the noise we used a recorder (Sony TCM-40DV) put in the incubator at 10 cm from the head of the baby, and reproduced two 5-minute periods of noise (recording periods 1a and 3a, respectively), separated by a 5minute silence period (recording period 2a). We recorded the values of babies skin temperature at the beginning and at the end of the experiments, using the electronic thermometer of the incubators applied on the thorax. We also studied whether HRV changes might be due to changes in vibrations (and not by EMF) produced by turning the motor on and off. We used a triaxial ICP accelerometer (PCB Piezotronics, USA) (sensitivity 10 mV/ms2) to measure vibrations according with the standard ISO 2631-at the mattress level when the motor was on and off. The signals from the accelerometer were simultaneously acquired by a digital spectrum analyser (Soundbook, Sinus, Germany) with four acquisition channels. We measured the vibration levels at six points of the incubator mattress: two points on the axial line of the mattress, two points on a line at 10 cm to the right of the axial line and two points on a line at 10 cm to the left of the axial line. This study was approved by the Siena Hospital ethics board. Informed consent was obtained from the babies parents.

MATERIALS AND METHODS

We studied 43 newborns in Siena hospital, between March and August 2007, during their stay in incubators. Exclusion criteria were major malformations, intraventricular haemorrhage greater than grade II, seizures, bradycardia (basal heart rate ,100/min) and tachycardia (basal heart rate.180/min). We performed two separate experiments. The first (experiment 1) assessed whether the EMF produced by incubators could alter newborns HRV. The second experiment (experiment 2) was begun after the positive results of experiment 1 and assessed whether HRV changes were due to the EMF or to changes in noise which, as well as EMF, was produced by the incubator motor. Different newborns took part in the two experiments. All babies were in quiet wakefulness, active sleep or quiet sleep; no baby was in active wakefulness or crying.

Experiment 1

We studied 27 babies confined to neonatal incubators for clinical reasons. Table 1 shows details of the babies studied. Before applying the electrodes, an EMF recorder (EMDEX Lite, Enertech, Campbell, CA, USA) measuring 4.7062.4061.00 (11.966.162.2 cm) was placed in the incubator on the mattress close to the babys chest, so that it was possible to see the display from the outside. The detection range of the EMDEX Lite is 0.1700 mG/401000 Hz. EMF levels were recorded by an observer in each period. We recorded 15-minute ECGs of the babies in supine position at least 1 hour after feeding. No baby was on assisted ventilation. A commercially available imaging system (Cardioline, Prima Holter; Remco, Vignate-Milano, Italy) was used. Five electrodes were gently applied to the babies thorax; after a 5-minute interval the 15-minute ECG was recorded. After 5 minutes of recording (recording period 1), the motor of the incubator was turned off for 5 minutes (recording period 2) and then was turned on again, recording for another 5 minutes (recording period 3).

Data analysis

Each ECG signal is usually acquired at a frequency of 250 samples/second. Detection of the QRS complex and measurement of the RR interval were performed automatically, using the R-wave peak as a reference point. Premature beats, missed beats and artefacts were identified visually using an interactive graphic interface, and evaluated by the operator. An RR tachogram, consisting of a discrete series of successive RR intervals as a function of the number of recognised QRS complexes, was obtained. HRV was evaluated by a frequency and time domain analysis.
Analysis of the frequency domain
The algorithm used to analyse the tachogram in the frequency domain was a spectral method (fast Fourier transform). According to Task Force of the European Society of Cardiology and the North American Society of Pacing Electrophysiology20 three main spectral components can be distinguished in a spectrum calculated from RR tachograms of 5 minutes: (a) a very low-frequency component (,0.04 Hz); (b) a low-frequency component (range 0.040.15 Hz); and (c) a high-frequency component (range 0.150.4 Hz). Measurements of the LF and HF power components as well as total power were made in absolute power units (ms2). The ratio of high to low frequency was calculated, as an expression of sympatho-vagal balance.

Experiment 2

To assess whether any changes in HRV might be due not to changes in the EMF but to changes in background noise (due to the arrest of the incubator fan), we studied 16 newborns (mean (SD) postmenstrual age 34.1 (2.4) weeks) with the same inclusion criteria used for experiment 1. We measured HRV in a 15 minute period during which we turned the incubator motor off and reproduced close to the babys head a noise of the same intensity and features (4850 dB, frequency range: Hz) as that
Table 2 Mean (SD) low-frequency (LF) and high-frequency (HF) heart rate variability during three recording periods: P1 (baseline registration with incubator motor on); P2 (5-minute registration with incubator motor off), P3 (5-minute registration with incubator motor on again)
HF* Median (range) LF/HF* Median (range) 2.0 (0.52.0) 1.5 (0.32.9) 2.5 (1.83.5) Total power* Median (range) 484 (812209) 1024 (1443696) 676 (1003969) Skin temperature Median (range) 36.6 (36.136.8) 36.7 (36.036.9) 36.5 (36.336.9)
Table 1 Characteristics of the babies studied

Experiment Male/female 16/11 9/7 Gestational age Median (range) 30 (2533) 31 (2436) Postmenstrual age Median (range) 34 (3038) 35 (3138)
P(7250) P(16619) P(10623) *p,0.05.
Arch Dis Child Fetal Neonatal Ed 2008;0:F1F4. doi:10.1136/adc.2007.132738

Statistical analysis

We analysed data, comparing spectral HRV parameters (mean total power, LF, HF and LF/HF) by the Wilcoxon matched-pairs signed-ranks test, by means of GraphPad Instat 3.05 software.
turning the incubator off caused a significant change in HRV and in sympatho-vagal balance, which returned suddenly to basal levels when the motor was turned on again. In particular, EMF caused a reduction in HRV and an increase in LF/HF ratio, an expression of sympathetic dominance. This is noteworthy for several clinical reasons: c A reduced HRV is a powerful and independent predictor of adverse prognosis in patients with heart disease and in the general population,27 and the proarrhythmic role exerted by transient or persistent alterations in sympathetic and vagal control mechanisms is well known.27 Specifically, sympathetic hyperactivity favours the onset of lifethreatening cardiac arrhythmias, whereas vagal activation usually exerts relatively protective antifibrillation effects.c The LF/HF ratio is higher in preterm infants than in adults ; but this may be influenced by the electromagnetic environment, leading to the need for new studies on babies not exposed to an EMF. c General criteria require that human physiological variables should never be influenced by external sources whose consequences are still unknown. An ecologically safe environment (ie, where involuntary influences on human organisms are not exerted by the equipment) should always be guaranteed, especially for premature infants whose tissues are made up of developing immature cells, particularly affected by external chemical and physical pollutants. 31 c Neonatal incubators are noisy : the presence of a high EMF is another factor that new engineering of incubators worth considering. c The question as to whether exposure to an EMF can cause leukaemia 32 remains unanswered and controversial. Nevertheless, results of increasingly sophisticated studies and two pooled analyses reported that the risks of leukaemia doubled in children exposed to fields.4 mG during the year before diagnosis, compared with children exposed to fields ,1 mG.These values are considerably lower than those recorded in our incubators; more studies are needed before a definite link between leukaemia or other human diseases and EMF exposure is cofirmed. This subject remains highly controversial. In recent papers we showed that an increase in the distance between the motor and the mattress,8 or the use of ferromagnetic panels,35 decreased the level of EMF exposure and that even caregivers should be concerned about the risks of EMF, since they are exposed to peaks of.10 mG when close to the incubators.36 In the incubators we analysed, the EMF values were within ICNIRP guidelines,37 but were considerably higher than those recommended for computer monitor magnetic field emissions38 and even higher than those recorded in the proximity of HT lines (10 mG at 40 m from the line)39 and domestic video screens.40 These observations suggest that newborns should be one case in which a policy of prudent avoidance of an EMF is warranted, perhaps because no study has so far excluded the possibility of negative consequences of their chronic exposition to a high EMF in incubators.41 International recommendations and laws set levels to safeguard the health of workers exposed to EMFs: newborns should be worthy of similar protection, and follow-up programmes of formerly premature babies should include the study of sympathetic activity development.

Competing interests: None. Ethics approval: Approved by the Siena Hospital ethics board. F3

RESULTS

All babies in our study had been fed within 1 hour and were in quiet wakefulness, active sleep or quiet sleep. No baby was in active wakefulness or crying. Only two babies during experiment 1 cried and for this reason were excluded from the study. All babies were examined in the afternoon. In experiment 1, the mean (SD) EMF intensity was 8.9 (2.2) mG, 0.7 (0.7) mG and 8.6 (2.0) mG for recording periods 1, 2 and 3, respectively. Total power (expression of total HRV) and the HF component (expression of vagal activity) significantly increased when the incubators were turned off (p,0.05), and the LF/HF ratio decreased, suggesting that the EMF may cause sympathetic imbalance (table 2). Base values were restored when the incubators were turned on again (table 2), with a significant increase in LF/HF and a significant decrease in total power and HF component with respect to period 2 (p,0.05). LF mean values increased but not at a significant extent from period 1 to 2, but from period 2 to 3 their decrease was significant (p = 0.03). Mean skin temperature before the experiment was not statistically different from the temperature after the experiment. During experiment 2 (table 3), no significant changes in HRV components were noticed when the HRV during noisy periods was compared with the HRV of silent periods. The values of experiment 2 were not significantly different from those recorded in phase 2 of experiment 1, when the incubator was off. Measurement of the vibrations produced by the motor showed that their spectral components (180 Hz) are in a range (0.0040.008 m/s2) which is below the threshold of human perception (0.010.02 m/s2).

DISCUSSION

Our study showed that an EMF present in neonatal incubators can alter HRV in newborns, though other studies,with some exceptions,19 did not find similar effects in adults. We excluded the possibility that these changes might be due either to skin temperature variations (which did not vary significantly throughout the test) or to changes in background noise (see experiment 2). We also excluded the possibility that these changes might be due to changes in background vibrations produced by the incubator motor because we showed that the level of vibrations produced by the motor is below the human perception threshold. The decrease in EMF determined by

Table 3 Mean (SD) low-frequency (LF) and high-frequency (HF) heart rate variability during three 5-minute recording periods: P1 (reproduced noise); P2 (silence); P3 (reproduced noise)
HF Median (range) P1 P2 P3 164.5 (10896) 140.5 (91035) 88.5 (41013) LF/HF Median (range) 1.2 (0.72.1) 1.3 (0.82.2) 1.2 (0.82.0) Total power Median (range) 900 (643481) 841 (64384) 600 (363721) Skin temperature Median (range) 36.55 (36.337) * 36.7 (36.336.8)
*This value of skin temperature was not recordable because the incubator and its thermometer were off during the experiment. So temperature was recorded only at the beginning of phase 1 and at the end of phase 3. No significant difference was noticed between periods.
What is already known on this topic
Newborns are exposed to high electromagnetic fields when in incubators. Electromagnetic fields are supposed to provoke health consequences in humans.

19. 20.

What this study adds

22. 23.

Electromagnetic fields generated by incubators can alter heart rate variability in newborns. This is a sign of an influx of electromagnetic fields into the newborns autonomic system. This factor should be considered when designing incubators.
24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41.

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