4. new instruments and technical tips

4. New instruments and technical tips

4. New Instruments and Technical Tips

1. Preface We released the standard configuration for DVTS at the first Asia Telemedicine Symposium

in Kyushu University Hospital on December, 2007. This standard configuration contains the knowledge which was developed in over one hundred events and over three hundred connected points. The equipment in this configuration is required for comfortable teleconferencing, and to help easy setup and reduce testing time and troubles. We will popularize this configuration and continue towards greater standardization in the future.

Index 1. Preface (above) 2. Equipment for DVTS

2.1 Standard configuration 2.2 Required equipment and details

3. Installation 3.1. Analog-digital video converter (ADVC) 3.2. Microphone 3.3. Audio amplifier 3.4. Video camera 3.5. Personal Computer for DVTS 3.6. Display 3.7. Loudspeaker 3.8. VPN router

4. DVTS setup 4.1 Install 4.2 Setup detail

5. Sound troubles 5.1 Mechanism of echo (loop back noise) 5.2 Avoiding echo 5.3 Self sound adjustment and checking (local test)

6. Improvements for high quality teleconferencing 6.1 Staff allocations and roles 6.2 Manners of sharing PC presentation 6.3 Configuration for live demonstration (Surgery, Endoscopy, etc.) 6.4 Types of microphone 6.5 Handling detail of audio amplifier 6.6 Echo canceller unit

7. Closing

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2. Equipment for DVTS 2.1 Standard configuration (Fig. 2-1)

*Features

-Flexible connection to existing environment in conference venue. -Fix sound problems caused by stereo source. -Checkable sound source of transmission and independent handling of transmission and reception sound. -Load-balanced local network connection by using two PCs for each DVTS PC. -Redundancy PC allocation against PC trouble. -Expansible to live demonstration like surgery and endoscopy.

Fig. 2-1 Standard configuration

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2.2 Required equipment and details 1. Analog-digital video converter (ADVC)

Canopus ADVC 110

Canopus Twinpact 100

Sony HVR-25J

Necessary functions -Digital video signal conversion from analog video signal (S-video or composite) -Acceptable NTSC/PAL signal -16bit sound format conversion

ADVC 110 fills all requirements above. Twinpact 100 fills above and accepts analog RGB signal additionally. DV recorder like a “Sony HVR-25J” has similar function as above.

2. Microphone

Audio-Technica Dynamic vocal

microphone PRO-100

Necessary functions -For vocal use, unidirectional, Dynamic type, power SW equipped(Vocal microphone for general use fills above.)

Many kinds of products are available and it is difficult to distinguish among them. Operation checks are necessary.

3. Audio amplifier

BEHRINGER XENYX 502

Yamaha MG102c

Audio-Technica AT-PMX5P

Necessary functions -Microphone connectable （Channel for microphone exist） -Wide GAIN(Trim) range (approx +10dBV to -50dBV) - Controllable Sound balance (BALknob)

Precaution: A “Line mixer” which is a device similar to an audio amplifier should be disabled, because it can not amplify microphone sound to a high enough level.

Operation checks are necessary.

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4. Video Camera Necessary functions

-NTSC signal support -Composite or S-video output - Fixable or tripod mountable Precaution: DVTS MCN (Quatre) accepts only NTSC signal but DVTS software accepts PAL at peer to peer connection.

5. Personal computer for DVTS (transmission and reception)

Necessary functions -IEEE1394 port (onboard or add-in board) -Connectable external display -Fast Ethernet connection over 100Mbps -Windows Xp model is recommended

(We had an experience running DVTS on a Windows Vista PC, but

DVTS does not officially support Windows Vista.)

Recommended Specifications： OS: Windows XP, CPU: Intel Pentium 4,

Celeron or AMD Athlon or later (over 2GHz), RAM: over 256M, Graphic card:

DirectX supported, Network card: over 100Mbps, IEEE1394 port: OHCI

compatible.

6. Display (Flat TV (LED, Plasma), Projector)

Necessary functions -Analog RGB or DVI input Display device is a very important factor for image quality. Typically, image quality of flat TV is better than projector one. We recommended using flat unless limitation of venue width, for example.

7. Loudspeaker

Necessary functions -Adequate output capability for venue size -Useable embedded speaker on TV or PA system equipped at venue -Not required to support “Stereo sound ” or “Surround sound”

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8. HUB (Non secure NW)・VPN router (Secure NW required for a live surgery demonstration）

VPN router is a fundamental device to ensure patient privacy at live demonstration like a surgery or endoscopy. We use “IPsec (Internet Protocol Security) ” for encrypted transmission. We support VPN routers which are sold by Allied Telesis co, Ltd , named “AR550S, AR570S (for Japan) and “AT-AR750S(world wide）

Using VPN routers provided by other companies is difficult because of compatibility among these products.

3. Installation 3.1 Analog-digital Video converter (ADVC)

・Connect composite or S-video output cable from video camera to input channel. ・Unable to use both image sources (composite/S-video) at the same time. (S-video preferred) ・Some ADVC has a switch to configure sound properties. Set sound property to 16bit/ 48kHz,

refer to instruction accompanying your ADVC. Tips: 12bit/32kHz: Sound format for dubbing 16bit/48kHz: Normal sound format An ADVC which converts to only 12 bit sound does not work at multi point connections.

3.2. Microphone No setup on this device but refer to the following section 3.3 for installation and operation

check. 3.3 Audio amplifier

A certain level of knowledge is required to configure this device because it has large number of switches and knobs. Here, we use MG102G (Yamaha co, Ltd.) as an example to explain installation. There are many kinds of products for sound control, but for basic operations there are not many differences among them. Apply these instructions to your device accordingly.

Refer to section 6.5 for details of each switch and knob. Minus one sound: the fundamental method of sound setting for teleconference A configuration which can control transmission and reception sound sources separately is an important point to avoid echo noise at teleconferences. “Minus one sound” means that the sound source from microphones in your local venue is sent through the DVTS transmission channel and both sound sources (microphone, reception sound) are sent to the loudspeaker.

“Quatre”, a DVTS multi connection server, sends back the minus one sound to each endpoint.

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The following figure shows a configuration example which controls transmission and reception sound in one audio amplifier using “Stereo channel (right and left)” Advantages of this configuration as listed below: ・Separately controllable transmission and reception sound. ・Selectable output sound source in local venue, either including the presenter’s voice or not. ・Easy adjustment for balancing transmission and reception sound level. It is especially difficult to maintain sound quality for the transmission without frequent sound monitoring. Therefore, you need to pay attention to the sound level not only at testing, but also in the meeting.

It will help you if you remember each sound source assignment as follows. Left: Local (Sound for Local venue) Right: Remote (Sound for Remote sites) Recommended Cables and Plugs (JVC: Victor company of Japan, Ltd.)

C1 JVC CN-207A (φ3.5 Stereo (St.) -> φ3.5Monoural (Mono) 1.5m)

C2 JVC AP-100A（φ3.5M Mono -> φ6.3 Mono Exchange plug)

C3 JVC AP-102A（φ6.3Mono-> RCA exchange plug)

C4 JVC CN-186G (RCA×1->RCA×2 3Ｍ)

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3.4 Video Camera We use SD (Standard definition) and NTSC signal for DVTS multipoint connection. If you want to use a video camera of HD (high definition) model, please check your camera’s

settings for SD outputting in advance. The functions listed below cause problems, so refer to instructions to disable them. -Auto power off (power off automatically after a certain period time)

Causes sudden black out in meetings. -Demonstration mode (causes various effects on the image like mosaic or sepia coloring) -On screen display (date, time)

3.5. Personal Computer for DVTS (Transmission and reception for each)

Refer to section 4 for IEEE1394 cable connection and DVTS software installation.

3.6 Display (Flat TV (LED, Plasma), Projector) Select input channel for connected source.

3.7. Loudspeaker

Use loudspeaker appropriate for the size of the venue. Embedded TV speakers are useable if they have sufficient quality.

We recommend combining both stereo channels of reception sound to monaural sound and inputting the source into each plug of stereo channel.

This configuration is shown in section 3.3 above. Additionally, check the sound balance on your PC to hear both stereo channels clearly.

＜Sound balance check＞

1) Open “Sound and Audio device” from the control panel. 2) Find the knobs named “Balance” and “Volume”. 3) Set Balance knob to center position and adjust the volume for your environments.

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<A caution for connecting the sound cable to the PC to pick up reception sound> φ 3.5 Stereo plugs (Stereo mini plugs) which are used for headphone output on PCs are very small

and sensitive to contact. If connected carelessly, some sound problems may occur such as one channel sound because of a bad connection or short circuit. Check the sound in advance to make sure both channels output correctly.

3.8. VPN router (as necessary)

Advanced configuration of the VPN router will be done remotely. Configure basic setting like the IP address in advance and put the VPN router online. Knowledge of networks and operation commands are required for VPN setup so

ask a network administrator to do this. 4. DVTS Setup

DVTS (Digital Video Transport System) is software developed by “WIDE Project” from 1998 that can transfer Digital Video (DV) signal through IP networks. Recently, versions of DVTS have been developed for different operating systems and released as freeware. DVTS provides a high quality, low cost movie transfer system with video cameras connected to

PCs by an IEEE 1394v cable and broadband network. 4.1 Download of DVTS installer

The DVTS installer is released at the URL below. http://www.sfc.wide.ad.jp/DVTS/index-j.html DVTS for Windows 0.0.2 (Development build) is the latest version for Windows XP as of

October, 2008. This installer includes DVTS for HDV (DV format for High Definition). See each icon carefully to use the correct version of DVTS

4.2 Setup of DVTS 1) Installation

Click the DVTS installer icon and follow prompts to install software. After installation three icons appear on your desktop as below. The two icons on the right are

for HDV so do not use them this time.

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2) The following setup window is displayed when you run DVTS software.

1) Transmission setup.

Input IP address for destination at (4) and select DV device at (5). Check preview monitor at (7) and push “Start send” at (8) to start sending. Default port No is 8000 and there is need change the settings at (1, 2, 3, 6)

DV device select at (5) and “Start Send button” at (8) do not work unless the DV device has

been detected by the PC. The following window appears if you connect a DV device and the PC detects the device

correctly. (for Windows XP)

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4) Reception setup

Check Monitor output at (3) and push “Start Receive” at (9) to start receiving. Use port No 8000 (default) unless there is reason for some other assignment. “IEEE1394 Output” at (4) is used for exporting the DV stream to the DV device connected at

the port. You have to prepare another DV device for the reception PC. (it is impossible to share the DV

device connected to the transmission PC).

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5. Sound problems 5.1 Mechanism of echo (loop back noise)

Echo is a critical problem which causes sound quality loss, in particular at teleconferences. “Echo (loop back)” is when the speaker’s voice is heard two times or more. This problem is

caused by sound sent from B to A through the microphone at B as shown in the following figure 5.1.

Mechanism of echo (Fig 5.1)

5.2 Avoiding echo

Using adequate equipment helps to reduce echo. The equipment that we recommended reduces the echo to a level that can be ignored. You can set both sound sources (transmission and reception) to a high enough level of quality if

you perform self adjustment and checking (local test) according to the following session 5.3. Additionally, turning off the microphone while it is not in use is effective against echo.

5.3 Self sound adjustment and checking (local test)

In fact, it is very common for beginners connecting to a remote site for the first time to not recognize that a sound problem exists on their site. This phenomenon is caused by a feature of DVTS, which means sound problems happen at the

remote site only. Because of this, it can be difficult to recognize sound problems. We have introduced a procedure to check and adjust sound for better quality at the time of

DVTS setup.

Fig 5.1 Mechanism of echo

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<Self sound adjustment and checking (local test)> 1) Set DVTS equipment at the venue of the real event. (Refer to fig. 2.1）

You can use private IP addresses for testing

2) Roughly adjust the microphone input level and speaker output level. Microphone input

Transmission sound (input from microphone） Gain (Trim) knob: set the position to around the 3 o’clock position, Level knob (Feeder): set position to 12 o’clock (Center)

Reception sound (Input from reception PC) Gain (Trim) knob: set position to around 9 o’clock, Level knob (Feeder): set position to 12 o’clock (Center)

Output part

Sound setting on reception PC: around the center position (depends on output specification) Loudspeaker: around the one third position. (there is no need to change the setting if the usual settings are available)

Speak into your microphone and check the sound from the loudspeaker.

Broken or distorted sound

The distance between the microphone and mouth may be too close. Microphones for conferences are not used for KARAOKE, so it is recommended that you keep a distance of around 5-10 cm. If this does not solve the problem, try to reduce the gain by half steps until the problem is fixed. Then adjust the sound level.

Low volume from the loudspeaker:

Increase the LEVEL knob of the microphone channel by half steps and check the sound level. If the LEVEL knob reaches the maximum, return the knob to the center position and increase the GAIN (TRIM) knob bit by bit for a rough adjustment. It is best to use the GAIN knob for rough adjustment and the LEVEL knob for fine adjustment.

High volume from loudspeaker:

Decrease the LEVEL knob of the microphone by half steps and check the sound level. If the LEVEL knob reaches the minimum, return the knob to the center position and decrease the GAIN (TRIM) knob bit by bit for a rough adjustment. It is best to use the GAIN knob for rough adjustment and the LEVEL knob for fine adjustment.

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Case with unadjustable GAIN and LEVEL knobs: Try to use the volume knob on the loudspeaker.

Echo (loopback noise) occurs when the volume is excessively high. We recommend adjusting the sound with an audio amplifier.

Before proceeding, perform the following checks.

Check 1: There is no noise from the loudspeaker. (hum noise, howling, etc.) Check 2: There is no broken or distorted voice. Check 3: Generally, the voice comes through the loudspeaker well.

Turn off your microphone before the next step 3) Start sending

Start sending from your local transmission PC to reception PC and start receiving at the reception PC

You can see your sending image in the reception PC if you set up DVTS correctly.

Troubleshooting for transmission problems is omitted from this session because it is included in network problems and other sections.

Check network settings and security software for DVTS PCs. Before proceeding, perform the following checks.

Check 4: There is no packet loss on reception PC (It must be Zero in local transmission.) Check 5: There is no noise or problem with the reception image Check 6: There is no unexpected noise from the loudspeaker

(There must be some misconfiguration if you hear howling from your loudspeaker) 4) Confirmation of reception sound

Turn on your microphone and speak into it. If you set up correctly, you may hear your voice twice (source from transmission and

reception) from the loudspeaker.

Problem case 1, hearing voice once: There is no reception sound from loudspeaker.

Try the following to solve the problem. Pull out the sound cable which connects to the headphone plug of the reception PC and check reception sound from built-in speaker or loudspeaker designed for PC. If you hear voice from the reception PC, you should check the connection between the

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reception PC and the audio amplifier. If not, check the transmission settings of the audio amplifier and the connection between ADVC and the audio amplifier.

Problem case 2, howling: There must be some misconfiguration on your audio amplifier with reception sound being

input for transmission Refer to section 3.3 for connection details.

Problem case 3, hearing voice twice and also hearing obvious echo (loopback noise)：

Do not use the microphone in front of the loudspeaker. Keep an appropriate distance from the loudspeaker. If you still hear echoing after that, you should reduce the volume of the loudspeaker and the GAIN of the microphone channel. Try to reduce the volume of the loudspeaker first.

Problem case 4, hearing the voice twice but low volume for the second voice (reception):

Adjust reception sound to same level as transmission using the GAIN and LEVEL knobs of the reception input in the same way as adjustment of microphone sound.

Problem case 5, hearing voice twice with slight echo：

It is difficult to remove echo noise without a special device like an echo canceller. A meeting can be made to be comfortable by using the switch on the microphone.

Before proceeding, perform the following checks. Check 7: Hearing a similar level voice twice. Check 8: There is an echo which causes problems in conversation. Check 9: No sound comes from the loudspeaker when you turn off the microphone.

5) Congratulations!

The test is finished successfully if all these items are checked. We believe that a system which passes this test completely will not make an echo at real use。

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6 Improvements for high quality teleconferencing 6.1 Staff allocations and roles

High quality teleconferencing relies on constant attention to sound level and camera handling. We recommend allocating at least two staff members and more than three staff members for

formal events. 1. Sound quality check and adjustment - Broken voice (input too high), sound level, advising microphone position, etc. 2. Camera handling - Video camera and Digital camera (for taking pictures) 3. Total management - Contact with other stations, presenter support, etc.

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6.2 Manners of sharing PC presentation

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6.3 Configuration for live demonstration (Surgery, Endoscopy etc.)

The “Video mixer” device is required for live demonstrations to switch between image sources. -Surgical view -Overhead view -Overview image taken by video camera

Fig. 6.3 Configuration for live demonstration

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6.4 Types of microphone Microphones can be classified according to their features as follows. 1) The difference in methods of converting sound to electrical signal: Dynamic vs. Condenser Dynamic type: Signal conversion is the reverse mechanism of a loudspeaker. It has a simple structure and requires electrical power and a battery. Endures heavy duty and a high input volume level. Condenser type: This kind of microphone is usually used for small devices like PC headsets or wireless microphones. It requires a low voltage electrical power for its internal preamplifier. It has the advantage being small with a fine sound quality but has the disadvantage of resisting high volume input.

Dynamic type Condenser type

Electrical power

Not required Required

（Battery or plug-in power）

Handling Robust Delicate compared to dynamic type

Size Fairly large Can be downsized easily

Sensitivity Intermediate (resists high sound

input) Sensitive (prone to distort with loud

input)

2) Difference in method of transmission: wired vs. wireless Both types of microphone have enough performance for teleconference with enough knowledge of features.

Wired Wireless

Price Reasonable(around $100） Expensive （few hundred

dollars）

Noise resistance Good Needs attention

Receiving unit Not needed Needed

Cabling Needed Not needed

Some noise might be caused by the venue environment when using a wireless microphone. There are many possible reasons for this kind of noise, such as depleted battery, radio wave interference from nearby devices, crossed link with another unit, etc. A sound setup in which you can regularly check outgoing sound will raise awareness of this noise.

3) Microphone sound input: unidirectional vs. omnidirectional In general, vocal microphones are sensitive to sounds from only one direction because of their unidirectional feature. On the other hand, flat shaped microphones which are used for teleconferencing are designed as

omnidirectional. Using these kinds of microphones with DVTS may cause echo (loop back).

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We recommend using normal vocal microphones with a power switch for avoiding sound problems. 6.5 Handling detail of audio amplifier

There are many kinds of audio amplifier products, and there can be many knobs for sound adjustment. Therefore, it can be difficult to handle these devices without knowledge or skill. This session explains the function of each knob and offers a sample configuration. We use the product MG102c (Yamaha co, Ltd.) as our example. Almost all deices provided by various companies have similar functions and knobs so this explanation should help you to handle your own device.

1) Input plug You should pay attention to not only the plug’s shape but also the input signal power. The left picture shows two types of plugs; the upper side, named the “XLR type”, which accepts balanced sound signal, and lower side, named the “TRS phone type”, which accepts balanced or unbalanced signal (depending on the device). You can

use either plug for short distance connection but if you want to connect from a longer distance (over 5 m), or if you hear some unexpected noise, it is better to use the XLR type. Each channel has an adequate sound level. For the microphone plug this is -40 to -50dBu. For the line plug this is -10dBu. If you want to set the input sound level to 0dBu, you have to amplify the microphone

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input to one hundredfold and the line input to threefold. Therefore, if you connect a microphone to the line input plug, you can not get enough level of source from the amplifier because of inadequate sound power for the input plug. You have to connect the microphone into input plugs which have a GAIN knob.

With regard to headsets (microphone) for use with PCs, almost all products use “Plug-in powered microphone (condenser type)” in them. It is not written clearly, but the microphone plug on PCs support plug-in powered device and supplies 1.5v electrical power. So if you connect this kind of microphone, it does not work well because of power supply.

Phantom power supply is a similar function to that above but there is no compatibility between them. It should be used only as a guide to distinguish microphone types that are small and light weight.

Mini-jack connector type devices should be plug-in powered. 2) Gain control Some devices describe this as “TRIM”. As mentioned above, sound levels are different among input signals. If you increase gain too much, it causes problems like distortion or loopback noise. Adequate adjustment is important for good sound. (The PEAK indicator lights only occasionally and briefly at the points of highest input.) 3) Equalizer The equalizer provides a boost or cut of up to 15db for 3 ranges of frequencies (HIGH 10 kHz, MID 2.5 kHz, LOW 100 Hz). However, this is not very useful for human voice, which only spans a frequency range of300 Hz to 3 kHz. This function is usually used for music instruments of a certain frequency, for fine adjustments like removing minor noise etc. Removing the origin of a noise is the first choice for noise removal. 4) AUX Sends Used for output level adjustment of the AUX send channel. 5) PAN/BAL PAN: Determines the stereo positioning of the channel signal on the Stereo L and R buses.

The center position sends the same sound level. BAL: Sets the balance between left and right channels. We can control transmission and reception signals separately with the PAN knob. 6) Level control

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Adjust the level of each channel signal and the balance between the various channels. Knobs that are not in use are turned off to reduce noise. 7): Monitor output Outputs the signals adjusted by the MONITOR/PHONES control 8） Stereo out (Main out) Outputs the signals adjusted by the STEREO Master control. 9) AUX sends plug Outputs the signal from the EFFECT (AUX) bus (4). 10) PHONES plug This plug is for connecting headphones, and outputs the same signal as the MONITOROUT jacks. 11) Level Meter This LED meter displays the level of the signal sent to the MONITOR jacks and the PHONES jack. The “0” segment corresponds to the nominal output level. The PEAK segment lights red when the output reaches the clipping level. 12） STEREO Master Control Adjusts the signal level sent to the STEREO OUT jacks. 6.6 Echo canceller unit

Conference systems which include an echo canceller, like Polycom, facilitate easy communication without sound adjustment.

However, echo cancellers are not listed as a required item for our activity. This is for the following reasons.

Cost We have to buy the device additionally.

Sound Quality In case of use with omnidirectional microphones, which are provided with TV conference systems, we have to consider microphone placement for speakers who located far away.

Performance There may be some performance problems, like less responsiveness at the beginning of speaking, or bad sound quality.

Noise In case of use with omnidirectional microphones which provided with conference system, it’s usual to keep unmated status. So these microphones sometime catch background sound accidentally.

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Basically, the echo canceller is an expensive device and requires a certain level of knowledge and equipment to get high performance. It might be a good option to consider installing if you have a chance to replace teleconference devices. However, if you prepare devices as described above, there should be sufficient performance with certain sound adjustments and microphone handling like switching on and off. The following cases are common matters which cause echo because of uncontrollable sound. Due to DV camera

Why couldn’t we use the internal microphone of the video camera? Why couldn’t we connect a microphone to the video camera?

The internal microphone is omnidirectional with auto gain control. So it adjusts sound from the loudspeaker as a very high input, causing echo noise. The auto gain control also works for microphones connected directly and causes echo by high input.

Due to microphone

Why couldn’t we use the microphone which is used for teleconferencing?

Microphones which are provided with TV conference systems are omnidirectional and sensitive, so these microphones are supposed to be used with TV conference systems.

7. Closing

It has been 3 years since I joined this activity. At that time, a stable connection was the most important concern for engineers. In fact, we had many experiences of teleconference with packets lost, and difficult conversation. However, network quality improved very rapidly and widely, allowing stable connections with many institutions. This brought about not only an improvement of hardware but also good relationships among network administrators in each country. On the other hand, local set up improvements, including equipment and engineers’ skills, still remain important issues even now. Many sound problems are caused by echo or broken sound. These problems give a negative impression with users that the sound quality of DVTS is inferior to TV conference systems like Polycom, even though DVTS has a high specification for sound quality. This problem is caused by a shortage of engineers and equipment for DVTS setup in each institution. This sort of infrastructure development is an aim for future popularization, but it is very difficult for hospitals to employ a full-time engineer.

Therefore, we will try to solve this problem by providing know-how for DVTS setup to hospital staff members (paramedical or medical informatics) for performing the local setup. We believe that these engineers will build this telemedicine activity up to real popularization.

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4. new instruments and technical tips

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