Tens of thousands of taxi drivers in Beijing have a tool that could become part of China's all-out security campaign for the Olympic Games. Their vehicles have microphones -- installed for driver safety -- that can be used to listen to passengers remotely.

The tiny listening devices, which are connected to a global positioning system able to track a cab's location by satellite, have been installed in almost all of the city's 70,000 taxis over the past three years, say taxi drivers and industry officials.

As with digital cameras used in cities such as London, Sydney or New York, the stated purpose of the microphones is to protect the driver. But whereas other countries can only record images, Beijing taxis can be remotely activated without the driver's knowledge to eavesdrop on passengers, according to drivers and Yaxon Networks Co., a Chinese company that makes some of the systems used in Beijing. The machines can even remotely shut off an engine.

Whether these microphones are used to spy on riders is unclear. Asked if police could listen in on conversations in taxis, a Beijing police official declined to comment, saying that such matters were 'confidential' and that they were 'not supposed to release such details to the public.'

China has launched a massive operation to protect the Games. Monday's deadly attack in Xinjiang on a police station underscored Beijing's worries that terrorists will attack the Olympics. The government says it has deployed about 110,000 police, troops and volunteers in Beijing to ensure security.

But Chinese authorities are also determined to thwart protesters or human-rights activists who might try to embarrass the government. Tax drivers have been told to watch for suspicious behavior and odd packages.

Security experts say there is little likelihood that all conversations in taxis are monitored. But the presence of microphones in a place most would consider private is a reminder that there are many ways for Chinese authorities to monitor people they are concerned about.

The U.S. State Department has warned visitors to the Olympics that no place is safe from eavesdropping. 'All visitors should be aware that they have no reasonable expectation of privacy in public or private locations,' the department said on March 20.

The State Department notice explains that all hotel rooms and offices 'are considered to be subject to on-site or remote technical monitoring at all times. Hotel rooms, residences and offices may be accessed at any time without the occupant's consent or knowledge.'

Security experts say that all phones in China can be tapped, including cellphones, which send out signals that can be used to track location. That capability can be crippled only by removing the battery. Ahead of the Games, Beijing has also been blanketed by surveillance video cameras, while neighborhood committees -- residents' representatives to the government -- have also been called in for the effort.

Similar GPS systems with microphones have been rolled out in other parts of China, where taxi drivers have been recruited in the broader security effort.

In the northeastern city of Shenyang, site for some Olympic soccer matches, police have recruited 38,000 taxi drivers as 'intelligence agents,' according to China's Xinhua news agency. Their cooperation is important because drivers travel widely and meet many people, said Liu Juntao, an official with Shenyang's transportation department, according to Xinhua. Police there are offering citizens a reward of 500,000 yuan, or roughly $73,000, for valid tips about any potential terror plots or planned sabotage by dissidents.

Several Beijing taxi companies declined to comment on the security aspect but said that the GPS helps track taxis and that the two-way microphones will be used for translating services. About a dozen taxi drivers said the microphones were installed about three years ago, when newer cabs were built without protective metal cages around the drivers. Cabbies can turn on the system and alert their dispatch center by touching a discreet button near the steering wheel.

Human-rights activists say they are concerned about the ability to listen to conversations with the devices, which appear unique to China.

'This seems to suggest an effort by the police or other security forces to eavesdrop on conversations of passengers, rather than for the immediate safety and security of the taxi driver. It's not as if thieves outline plans to rob someone right before they do it,' said Phelim Kine of Human Rights Watch.

One Beijing taxi driver said he would be uncomfortable if the device in his vehicle could snap pictures of the riders. 'I wouldn't want to take a photo of my passengers without their knowledge,' said the driver, wearing the new shirt and tie the drivers are required to don during the Olympics. 'Wouldn't that violate their human rights?'

Yaxon Networks, based in Xiamen in Fujian province, says on its Web site that its GPS devices allow the police or a service center to 'judge if the driver is in danger' through remote surveillance or wiretapping. If it is necessary, the service center can immobilize a taxi remotely by 'cutting off the oil or electric supply,' the company adds.

As part of its security mobilization, China's military has deployed 34,000 soldiers in Beijing and other cities hosting Olympic events, Senior Col. Tian Yixiang, a senior official at the Olympic security command center told reporters Friday. The military says it has deployed antiaircraft missiles near Games venues and has dedicated 74 jets, 47 helicoptears and 33 ships to Olympic security duties.

'Generally speaking, Chinese strengths really lie in pre-empting threats rather than in crisis management or emergency response in the event that there really are any incidents,' said Bonnie S. Glaser, an expert on Chinese security at the Center for Strategic and International Studies, a private Washington think tank. She mentioned China's use of the microphones in taxis at a news conference in Washington in advance of President George W. Bush's arrival in Beijing on Thursday.

北京数万辆出租车上安装的小装置有可能成为中国奥运安保行动的一个组成部分。这些原本用于保护司机人身安全的微型麦克风可以用来远距离监听乘客的谈话。

据出租车司机和业内人士称，过去三年中，北京的7万辆出租车几乎都装上了这种小型监听设备。这种装置与一个能通过卫星跟踪出租车方位的全球定位系统(GPS)相连。

与伦敦、悉尼或纽约等城市使用数码相机时所宣称的一样，北京使用麦克风也说是为了保护司机的安全。不过其他国家的装置都只能记录图像，而据出租车司机和该系统的生产商之一、中国公司雅迅网络(Yaxon Networks Co.)称，北京出租车的这种系统能在司机不知情的情况下被远距离启动监听功能。这种装置甚至可以遥控汽车熄火。

目前尚不清楚这些麦克风是否被用来监听乘客谈话。记者询问北京警方一位人士，警方是否能监听出租车中的对话，该人士拒绝置评，并说这类事情是“保密的”，按规定他们“不能向公众透露这类细节”。

中国为保障奥运会安全发起了一场大规模行动。周一新疆发生的严重袭警案件更是凸显了北京恐怖分子会攻击奥运会。政府表示已在北京部署了11万安保人员，包括警察、军队和志愿者。

不过，中国有关部门也决心挫败那些可能试图让政府陷入尴尬的抗议者和人权活动人士。出租车司机被告知要密切注意可疑行为和包裹。

安保专家表示，有关部门不太可能会对出租车中的所有对话进行监听。不过，在被大部分人视为私人空间的出租车里安装麦克风的举动提醒人们，政府有很多方法来监控令他们担忧的人。

美国国务院(U.S. State Department)已经警告来北京观看奥运会的游客，任何地方都可能被监听。它在3月20日表示，所有游客都应该明白，不要理所当然地认为在公共或是私人场所能有隐私。

美国国务院的通知解释说，所有的酒店房间和办公室“任何时候都可能受到现场或是远距离技术监控。酒店房间、住所和办公室可能会在未经入住者同意或在入住者不知情的情况下随时被监听”。

安保专家表示，中国所有的电话都能被监听，包括手机。手机发送的信号能被用来跟踪方位，除非取出电池。奥运在即，北京各处都安装了监视器，社区居委会也被组织起来参与安保行动。

中国其他一些城市的出租车也安装了配有麦克风的GPS系统，出租车司机被招募成为奥运安保情报员。

据新华社报导，在举办部分奥运足球比赛的沈阳市，警方招募了3.8万名出租车司机做“治安情报员”。报导称，沈阳市交通局官员刘军涛（音）说，出租车司机的配合非常重要，因为他们活动范围很广，遇到的人很多。对恐怖活动和异见人士策划的破坏活动提供可靠线索的举报人将获得沈阳警方50万元人民币的奖励。

数家北京出租车公司拒绝对安保问题置评，不过他们表示GPS能帮助跟踪出租车的方位，双向麦克风会被用于语言翻译服务。大约有十多名出租车司机说，麦克风大约是三年前安装的，当时较新的出租车没有安装保护司机的铁护栏。一旦发生危险，司机可以打开系统，按方向盘旁边的一个隐秘的按钮，向调度中心发出警报。

人权活动人士称，他们对这个装置能被用来监听乘客对话表示担忧。在出租车上安装这种装置似乎是中国特有的。

人权观察(Human Rights Watch)的凯恩(Phelim Kine)说，这似乎是警方或其他安保机构试图窃听乘客的对话，而不是为了保护出租车司机的安全；好像窃贼们不会在抢劫前一分钟才作计划。

北京一位出租车司机说，如果车里的装置能拍摄乘客的照片，他会感到不安。这位按北京统一规定穿着新衬衫和领带的司机说：“我不想在乘客不知情的情况下，拍他们的照片；这不是侵犯他们的人权吗？”。

总部位于福建厦门的雅迅网络在公司网站上称，该公司生产的GPS通过远距离监视或是监听，能帮助警方或是服务中心判断司机是否处于危险中；在必要的时候，服务中心可以远距离切断油路或是供电，使出租车停下来。

奥运安保指挥中心高级官员田义祥大校上周五对记者说，作为安保工作的一部分，中国军方在北京和其他奥运协办城市派驻了3.4万名士兵。军方表示，已经在奥运场馆附近部署了防空导弹，并指定74架喷气机、47架直升机和33艘舰艇负责安保工作。

华盛顿私人智库国际战略研究中心(Center for Strategic and International Studies)中国安保问题专家葛来仪(Bonnie S. Glaser)说，总体来讲，中国的优势是防范威胁，而不是在真出现情况的时候进行危机管理或是应急反应。在布什4日出访亚洲（包括中国）之前，她在华盛顿的一个新闻发布会上提到了中国在出租车上使用麦克风一事。