CN1205821A - 用于检测电话分机摘机情况的调制解调器环路电流监测系统 - Google Patents

用于检测电话分机摘机情况的调制解调器环路电流监测系统 Download PDF

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CN1205821A
CN1205821A CN96199239A CN96199239A CN1205821A CN 1205821 A CN1205821 A CN 1205821A CN 96199239 A CN96199239 A CN 96199239A CN 96199239 A CN96199239 A CN 96199239A CN 1205821 A CN1205821 A CN 1205821A
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R·A·皮特施
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Technicolor USA Inc
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Abstract

电话线路监视电路使用光隔离器(OPTO2),以便把电话线路电流转换为加到A/D变换器(118)的输入端的电压。A/D值是代表电话线路电流的粗略值。A/D在预定间隔期间被采样,以便识别由电话公司中央局引入的变化,以及当确定电话分机已被摘机时考虑这些变化。当用户使电话分机摘机时,线路电流在电话分机和IRD调制解调器(100)之间分流,并检测到这样的变化。

Description

用于检测电话分机摘机情况的调制 解调器环路电流监测系统
发明领域
本发明总的涉及电话线路监视电路领域。
发明背景
现代卫星通信系统，例如，由汤姆逊消费电子公司(ThomsonConsumer Electronics Inc．)印第安纳波里斯，印第安纳(Indianapolis，Indiana)制造的RCADSS系统，包括用于自动呼叫预定电话号码的电路，以便报告有关使用用户集成接收机译码器(IRD)的能计费特性。当然，这样的计费是必须的，因为用户通过向若干个程序提供者中的一个或多个进行预订而接收到编程程序。不幸的是，没有保证IRD接入到电话线路的日期时间，因为用户确实可能在任何时间发起呼叫(例如，人们不能为紧急事件安排日程表)。因此，希望能检测用户拿起分机电话机的情况，以便IRD可释放线路给用户。然而，由于电话公司所提供的电压状态的漂移，电话线路监视电路的工作往往是不符要求的。会有许多因素影响送到用户家中的电话电压电平，例如，离中央局的线路距离，中央局使用的的线路卡上的信号中的起伏，到用户家中的连接是否已被浸蚀，等等。现在的问题是，在假定线路电平的改变是正常值的实际情况下，如何精确确定电话分机是否被摘机(从而造成对线路电压电平的扰动)。
而且，由于人们不可能可靠地在用户位置处测量相对用户的接地基准的电话线路电压而不冒引入接地环路电压的风险，因而测量工作显得更为复杂。也必须指出，因为耦合到电话网络的设备需要具有相对较高的输入阻抗，所以这些设备容易受到拾取噪声瞬态现象的影响，这些噪声瞬态现象会干扰对电话线路电平的测量。
发明概要
电话线路监视电路使用光隔离器，以便把电话线路电流转换为加到A／D变换器的输入端的电压。A／D值是代表电话线路电流的粗略值。A／D在预定间隔期间被采样，以便识别由电话公司中央局引入的变化，以及当确定电话分机已被摘机时考虑这些变化。当用户使电话分机摘机时，线路电流在电话分机和IRD调制解调器之间分流，并检测到这样的变化。
附图简述
图1显示适用于本发明的电话线路监视电路；
图2显示了在理解本发明时有用的线路电流数值和A／D读数表；以及
图3显示按照本发明的电话线路监视电路的替换实施例。
附图详述
现在将参照附图描述具有检测电话分机摘机的能力的电话线路监视电路。
参照图1，二极管电桥装置BR1通过塞尖(TIP)和塞环(RING)端口被连接到电话网络(未示出)，用于提供去到消费者电子设备的通信和来自消费者电子设备的通信，其有关部分显示于图1。由TECCOR公司制造的Sidactor，(双向二端交流开关元件)S1被跨接到电桥BR1的正端和负端，以便保护进一步连接到电桥的电路。概略地，Sidactor是具有一种运算特性的保护装置，在达到击穿电压后随着通过设备的电流增加，它的阻抗下降。在图1的装置中它的功能是限制在OPTO1上建立的电压。OPTO1是达林顿光隔离器，它被用作为“挂钩开关(hook-switch)”的电子等价物，用于把该设备连接到电话网以便建立呼叫。OPTO1在系统控制微计算机(μC)110的控制下运行。术语“微计算机”、控制器和“微处理器”，在这里使用时是等价的。也可看到，微计算机110的控制功能可由为此特定目的专门制作的集成电路(即，用户芯片)来完成，且术语“控制器”在这里使用时也打算包括这样的器件。微计算机110包括中央处理单元(CPU)112和编程存储器(ROM)116，并把短期数据存储在随机存取存储器(RAM)114中。RAM114可以是在微计算机110的内部或外部，并且也可以是易失性或非易失性类型。术语“RAM”114也打算包括电可擦可编程只读存储器(EEPROM)。本领域技术人员将看到，如果利用易失性存储器，则可能希望使用适当形式的备用电源(例如备用电池)，以便当电源失效时保留其内容。
光隔离器OPTO1通过隔离变压器T1把信号耦合到调制解调器100和耦合来自调制解调器100的信号。出现在变压器T1的初级线圈上的电话公司环路电流也通过电阻R1加到第二光隔离器OPTO2。OPTO2把环路电流转换成建立在其发射极电阻R3上的输出电压。输出电压被加到包括电阻R4和二极管D4的装置上，也加到被包括在微计算机110中的A／D变换器118的输入端。本领域的技术人员将注意到，A／D变换器也可位于微计算机110之外，并连接到该计算机。电阻R4和二极管D4的装置的有利之处在于，直到二极管D4的正向电压出现之前电阻R4在该电路中是被断开的。在R4和D4的支路连通时，电阻R3和R4几乎是并联的。
如前所述，人们不能把电话公司提供的线路电压考虑为任何特定值。事实上，它可涵盖宽范围的数值。另外，电话线路监视电路必须被设计成确保在所有条件下中央局的正确操作。应用到这个设计的一个约束条件是，在20毫安直流(DC)时，该电路对于电话网必须呈现不大于300欧的阻抗。另一种叙述这个要求的方式是，输入阻抗应满足：在20毫安的电流时应该在其上建立不大于6伏的电压。二极管D1，D2，D3的串联结构被跨接在电阻R1和光隔离器OPTO2之间。二极管D1，D2，和D3把光隔离器OPTO2上的电压限制为一个能确保OPTO2在高电话线路电压条件下将不被击穿的数值。二极管D1，D2，和D3上的电压降按照通过它们的电流而改变。电阻R2用来降低在低电流(即，20毫安)运行下二极管D1，D2，和D3串联结构上的电压。这确保了在低电流条件下中央局脉冲拨号的正常运行。
在运行时，电话线路环路电流按有规律的时间间隔被连续监视。电流检测器(光隔离器OPTO2)提供一个代表通过环路的电流大小的信号给A／D变换器118。如果电流显著地下降，则控制器110确定用户电话分机被摘机，然后，控制器中止，以便不干扰用户电话呼叫。
图2的表给出了环路电流数值表和相应的载波检测器输出电压，以及用于判定电话分机是否已摘机的推荐的触发点。应当指出，如果环路电流相对较低(18毫安或更小)，则通过监视电压来检测分机摘机变成为不可靠的。然而，联邦通信委员会(FCC)规定了要由电话业务提供者提供的最小的长环路电流为23毫安。正如人们从图1的表中很容易地看到那样，图1的电路仍旧以小到20毫安的环路电流(比最小允许电流小3毫安)提供可靠的触发点。也要指出，由电话公司提供的电流可高达120毫安。本发明利用了这样的认识，从而提供多个“触发点”(特定电压电平)，它包容这样的宽范围以便可靠地指示电话分机已被摘机。
图3显示本发明的替换实施例，其中二极管D1，D2，D3和电阻R2已由包括晶体管Q301和电阻R305，R306，R307在内的晶体管装置所代替。可以看到，晶体管装置可提供电话线路电流到输出电压的更线性的转换，但或许以稍高的花费为代价。
R301(和图1的R1)优选地是560欧，R303(和R3)优选地是15千欧。R304(和R4)优选地是1．5千欧。电阻R305和电阻R306(以及图1的R2)的典型值是68欧。这个值是重要的，如果选择相对较高的电阻值，则造成一个大于先前提及的在20毫安输入电流时的6伏的电压。发射极电阻R307优选地是7．5欧。Q301可以是通常可得到的2N3904晶体管。

Claims (8)

1．一种电话线路监视电路，包括：
电话线路连接装置，用于把信号耦合到电话网或耦合来自电话网的信号；
调制解调器装置，用于通过所述连接装置与所述电话网通信；
控制装置，用于提供控制信号；
转换装置，用于把电话线路电流转换成正比于所述电流的电压；
A／D变换器装置，用于采样所述电压并提供数字样本给所述控制装置；
其中所述控制装置监视来自所述A／D变换器装置的所述样本，并从相继的读数之间的偏差值来确定连接到所述电话线路的电话分机是否摘机。
2．权利要求1的电路，其特征在于，其中所述转换装置是光隔离装置。
3．权利要求2的电路，其特征在于，还包括跨接在所述光隔离装置的电压限制装置，用于限制在所述光隔离装置上建立的电压。
4．权利要求3的电路，其特征在于，其中所述电压限制装置包括多个串联的二极管。
5．权利要求4的电路，其特征在于，还包括跨接在所述二极管装置和所述光隔离装置上的电阻装置，用于在低电流工作期间限制在所述二极管装置上建立的电压。
6．权利要求5的电路，其特征在于，还包括在所述控制装置控制下的挂钩开关装置，用于建立到所述电话网的连接。
7．权利要求3的电路，其特征在于，其中所述电压限制装置包括由晶体管装置和电阻装置组成的装置，其中所述电阻装置和所述晶体管装置的主传导路径串联连接，并和所述光隔离装置并联连接。
8．权利要求7的电路，其特征在于，还包括在所述控制装置控制下的挂钩开关装置，用于建立到所述电话网的连接。
CN96199239A 1995-12-22 1996-12-18 用于检测电话分机摘机情况的调制解调器环路电流监测系统 Expired - Lifetime CN1095269C (zh)

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GBGB9613608.0A GB9613608D0 (en) 1996-06-28 1996-06-28 40mhz VCXO and loop filter for digital symbol lock timing for high speed modems

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CN102132332B (zh) * 2008-08-20 2013-08-07 西门子工业公司 传送音频及直流信号的装置及方法

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DE69604596D1 (de) 1999-11-11
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AU715450B2 (en) 2000-02-03
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BR9612176A (pt) 1999-07-13
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WO1997023987A1 (en) 1997-07-03
CN1209243A (zh) 1999-02-24
KR100408983B1 (ko) 2004-03-24
US6442255B1 (en) 2002-08-27
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