主要用在商品住宅楼，通过呼叫，进行可视对话，确定来访身份。
在，可视门铃作为便捷的实用产品，从九十年代末至今，主要应用在商品住宅楼，规模迅速发展，目前已经普遍进入城市小区中高层住宅。使用时，住户听到铃声，像接听可视电话一样，接受来访者通过楼下门口主机的呼叫，进行对话，同时住户家中的可视分机可通过楼下主机摄像头接收视频影像，住户观察分机显示屏幕上的监控图像确认来访者的身份，后决定是否按下室内分机的开锁按钮，打开连接门口主机的电控门锁，允许来访客人开门进入。
可视门铃，运用在一栋或多栋住宅楼中，多个住户共同使用一个门口主机中，通常被称之为可视对讲系统、楼宇可视对讲系统；而运用在单个住户中，如别墅，通常被称之为独户可视门铃或别墅可视门铃。
可视门铃目前在全球各地的城市住宅中，已经普遍使用，它的生产制造商主要集中在安全防范行业相对发达的广东省深圳、广州和福建省的厦门等城市。
可视对讲系统是小康住宅服务措施，提供访客与住户之间双向可视通话，达到图像、语音双重识别从而增加安全可靠性，同时节省大量的时间，提高了工作效率。更重要的是，一旦住家内所安装的门磁开头、红外报警探测器、烟雾探险测器、瓦斯报警器等设备连接到可视对讲系统的保全型室内机上以后，可视对讲系统升级为一个安全技术防范网路，它可以与住宅小区物业管理中心或小区警卫有线或无线通讯，从而起到防盗、防灾、防煤气泄漏等安全保护作用，为屋主的生命财产安全提供大程度的保障。它可提高住宅的整体管理和服务水平，创造安全社区居住环境，因此逐步成为小康住宅不可缺少的配套设备。
可视门铃系统是一种用于高层住宅、公寓大厦内外，户间信息传递，防盗门控制和在紧急情况下住户向楼宇值班室报警的设备。它以功能齐全、性能可靠、其容量大、造型美观、安装使用方便而深受广大用户欢迎，并且也在安全生活小区中得到了广泛的应用。
一、可视门铃系统工作原理
来访者可通过楼下单元门前的主机方便地呼叫住户并与其对话，住户在户内控制单元门的启闭，小区的主机可以随时接收住户报警信号传给值班主机通知小区保卫人员，系统不仅增强了高层住宅安全保卫工作，而且方便了住户，减少许多不必要的上下楼麻烦。
二、可视对讲系统的工作方式
楼门平时总处于闭锁状态，避免非本楼人员在未经允许的情况下进入楼内，本楼内的住户可以用钥匙自由的出入大楼。当有客人来访时，客人需在楼门外的对讲主机键盘上按出欲访住户的房间号，呼叫欲访住户的对讲分机。被访住户的主人通过对讲设备与来访者进行双向通话或可视通话，通过来访者的声音或图像确认来访者的身份。确认可以允许来访者进入后，住户的主人利用对讲分机上的开锁按键，控制大楼入口门上的电控门锁打开，来访客人方可进入楼内。来访客人进入楼后，楼门自动闭锁。
住宅小区物业管理的安全保卫部门通过小区安全对讲管理主机，可以对小区内各住宅楼安全对讲系统的工作情况进行监视。如有住宅楼入口门被非法打开、安全对讲主机或线路出现故障，小区安全对讲管理主机会发出报警信号、显示出报警的内容及地点。小区物业管理部门与住户或住户与住户之间可以用该系统相互进行通话。如物业部门通知住户交各种费用、住户通知物业管理部门对住宅设施进行维修、住户在紧急情况下向小区的管理人员或邻里报警求救等。
系统主要由主机、分机、UPS电源、电控锁、、保护器、视频放大器、信号中继器、讯号转换器、视频切换器、主机选择器、网络汇总器、集线器、数字信号转换器、光端机和闭门器等组成。根据类型可分为直按式、数码式、数码式户户通、直按式可视对讲、数码式可视对讲、数码式户户通可视对讲等。
门口机
门口机
主机
主机是可视门铃系统的控制部分，每一户分机的传输信号以及电锁控制信号等都通过主机的控制，它的电路板采用减振安装，并进行防潮处理，抗振防潮能力强，并带有夜间照明装置，外形美观、大方。
分机
分机是一种对讲话机，一般都是与主机进行对讲，但现在的户户通可视门铃系统则与主机配合成一套内部电话系统可以完成系统内个用户的电话
室内七寸分机
室内七寸分机
联系，使用更加方便，它分为可视分机，非可视分机。具有电锁控制功能和监视功能，一般安装在用户家里的门口处，主要方便住户与来访者对讲交谈。
UPS电源
它的功能主要是保持可视门铃系统不掉电。正常情况下，处于充电的状态。当停电的时候，UPS电源处于给系统供电的状态。现在可视门铃系统，厂家一般不配备UPS电池，主要是可视系统耗电太大，一般的小容量UPS电池保证不了使用时间！
、保护器、视频放大器、信号中继器
与保护器在总线制系统中使用，功能为呼叫信号提供寻址接通室内机。保护器功能主要为户内线路短路提供隔离保护作用或提供部分线路信号处理功能。视频放大器用于线路视频信号处理以满足视频远距离传输时视频质量的要求，信号中继器为总线控制信号远距离传输有衰减或干扰时选用。 为使用更方便可靠，某些与保护器功能设计在一起，种类有多种，不同系统或不同功能要求的工程可选择不一样的型号的，典型系统按其功能主要有单路纯解码、四路半隔离、四路隔离保护带
视频信号处理、四路普通联网、四路全隔离带视频处理联网型及多路的多功能，当系统需求较多附加功能的时，如果只选择普通，会影响系统性能，选用时可向厂家咨询或查询系统产品说明书。
讯号转换器、视频切换器
讯号转换器用于非直接联网主机的信号转换为联网信号的中间网络设备，在某主机本身具备联网线接口的情 况下，不需要专用的讯号转换器产品。视频切换器用于个别系统联网时将单元视频信号切换至联网总线视频线上,以更好地提高联网视频信号的点对点传输质量。
主机选择器
若某楼道有多个出入口都需要安装门口主机时，若所选择的门口主机本身不带多门口机并联功能，则可通过此设备实现多个门口主机工作时的信号切换作用；若所选择的门口主机本身带有多门口机并联功能，则本设备不需要使用。
网络汇总器、集线器、数字信号转换器、光端机
大型小区联网时，信号在传输中有衰减或受干扰，并且接线较多，通过此类设备，可大程度的还原失真的信号，以满足远距离传输，个别模拟信号超远距离传输需用数字TCP/IP转换器或光端机进行传输，以达效果更佳。
电锁
品种很多，常用的有电控锁、磁力锁、静音锁、电机锁等等。一般内部结构主要由电磁机构组成。用户只要按下分机上的电锁键能使电磁线圈通电，从而使电磁机构带动连杆动作，能控制大门的打开。
闭门器
它是一种特殊的自动闭门连杆机构。它具有调节器，可以调节加速度和作用力度，使用方便、灵活。
软件技术
大部分需要用到音视频交互的可视门铃系统都可以采用AnyChat 开发。AnyChat 内部封装了音视频的采集、编码、传输、解码以及播放（显示）功能，只需要几个简单的API调用，即可实现多个用户之间的语音、视频、文字交互，由于内核已经实现了P2P网络，所以上层应用不需要关心复杂的网络传输问题，简化了上层应用的开发难度，上层应用的开发人员可以把更多的精力投入到业务流程、用户体验等方面，实现应用系统的快速开发。
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David Copperfield
prospects. Papa was very much depressed then, and more bowed
down by care than ever you or I have seen him; but he seemed
relieved by this expedient of the partnership, though at the same
time he seemed hurt by it and ashamed of it.’
‘And how did you receive it, Agnes?’
‘I did, Trotwood,’ she replied, ‘what I hope was right. Feeling
sure that it was necessary for papa’s peace that the sacrifice
should be made, I entreated him to make it. I said it would lighten
the load of his life—I hope it will!—and that it would give me
increased opportunities of being his companion. Oh, Trotwood!’
cried Agnes, putting her hands before her face, as her tears started
on it, ‘I almost feel as if I had been papa’s enemy, instead of his
loving child. For I know how he has altered, in his devotion to me.
I know how he has narrowed the circle of his sympathies and
duties, in the concentration of his whole mind upon me. I know
what a multitude of things he has shut out for my sake, and how
his anxious thoughts of me have shadowed his life, and weakened
his strength and energy, by turning them always upon one idea. If
I could ever set this right! If I could ever work out his restoration,
as I have so innocently been the cause of his decline!’
I had never before seen Agnes cry. I had seen tears in her eyes
when I had brought new honours home from school, and I had
seen them there when we last spoke about her father, and I had
seen her turn her gentle head aside when we took leave of one
another; but I had never seen her grieve like this. It made me so
sorry that I could only say, in a foolish, helpless manner, ‘Pray,
Agnes, don’t! Don’t, my dear sister!’
But Agnes was too superior to me in character and purpose, as
I know well now, whatever I might know or not know then, to be
Charles Dickens ElecBook Classics
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David Copperfield
long in need of my entreaties. The beautiful, calm manner, which
makes her so different in my remembrance from everybody else,
came back again, as if a cloud had passed from a serene sky.
‘We are not likely to remain alone much longer,’ said Agnes,
‘and while I have an opportunity, let me earnestly entreat you,
Trotwood, to be friendly to Uriah. Don’t repel him. Don’t resent
(as I think you have a general disposition to do) what may be
uncongenial to you in him. He may not deserve it, for we know no
certain ill of him. In any case, think first of papa and me!’
Agnes had no time to say more, for the room door opened, and
Mrs. Waterbrook, who was a large lady—or who wore a large
dress: I don’t exactly know which, for I don’t know which was
dress and which was lady—came sailing in. I had a dim
recollection of having seen her at the theatre, as if I had seen her
in a pale magic lantern; but she appeared to remember me
perfectly, and still to suspect me of being in a state of intoxication.
Finding by degrees, however, that I was sober, and (I hope) that
I was a modest young gentleman, Mrs. Waterbrook softened
towards me considerably, and inquired, firstly, if I went much into
the parks, and secondly, if I went much into society. On my
replying to both these questions in the negative, it occurred to me
that I fell again in her good opinion; but she concealed the fact
gracefully, and invited me to dinner next day. I accepted the
invitation, and took my leave, making a call on Uriah in the office
as I went out, and l
