PFSK152 3BSE018877R2 3BSC980006R361模塊卡件
通常需要通過(guò)將CT連接到RTS或一些+12伏電源，如圖A-1所示的電阻器。
電流互感器也經(jīng)常跨接至MC1488門(mén)，該門(mén)具有輸入接地（為此提供柵極）。
許多系統(tǒng)中使用的另一個(gè)信號(hào)是DCD。最初的目的該信號(hào)的目的是通知系統(tǒng)來(lái)自正在接收遠(yuǎn)程調(diào)制解調(diào)器。該信號(hào)經(jīng)常使用由軟件顯示信息，如承運(yùn)人不在場(chǎng)幫助用戶診斷通信故障。顯然，如果系統(tǒng)正確設(shè)計(jì)為使用該信號(hào)，且未連接對(duì)于調(diào)制解調(diào)器，信號(hào)必須由上拉電阻器或閘門(mén)如上所述（見(jiàn)圖A-1）。許多調(diào)制解調(diào)器期望DTR高信號(hào)并發(fā)出DSR響應(yīng)。
PFSK152 3BSE018877R2 3BSC980006R361模塊卡件軟件使用這些信號(hào)來(lái)幫助提示操作員關(guān)于可能的故障原因。有時(shí)使用DTR信號(hào)斷開(kāi)電話電路以準(zhǔn)備另一個(gè)自動(dòng)呼叫這些信號(hào)是與所有人通信所必需的可能的調(diào)制解調(diào)器（見(jiàn)圖A-1）。示例配置圖A-1是一個(gè)良好的中間道路配置，幾乎始終有效。如果未從接收到CT和DCD信號(hào)調(diào)制解調(diào)器，跳線可以移動(dòng)以人為提供需要的信號(hào)。圖A-2顯示了連接EIA-232-D連接器以啟用一種僅用三條線連接到基本終端的計(jì)算機(jī)。這是可行的，因?yàn)榇蠖鄶?shù)終端都有DTR和RTS信號(hào)開(kāi)啟，可用于拉起CT、DCD和DSR信號(hào)。可以使用其中兩個(gè)背靠背接線的連接器。在這個(gè)然而，在實(shí)現(xiàn)過(guò)程中，診斷消息可能會(huì)否則不會(huì)生成，因?yàn)樗形帐侄际抢@過(guò)。此外，TX和RX線路可能必須交叉因?yàn)閬?lái)自終端的發(fā)送是傳出的，但調(diào)制解調(diào)器上的發(fā)送線路是輸入信號(hào)。另一個(gè)需要考慮的問(wèn)題是接地引腳的使用。有兩個(gè)標(biāo)有GND的引腳。針腳7是信號(hào)接地，必須連接到遠(yuǎn)程設(shè)備以完成電路。針腳1是底盤(pán)接地，但必須小心使用。機(jī)箱是通過(guò)中的綠色導(dǎo)線連接到電源接地電源線和必須連接到機(jī)箱才能進(jìn)入符合電氣規(guī)范。
usually necessary to make CTS high by connecting it to RTS or to
some source of +12 volts such as the resistors shown in Figure A-1.
CTS is also frequently jumpered to an MC1488 gate which has its
inputs grounded (the gate is provided for this purpose).
Another signal used in many systems is DCD. The original purpose
of this signal was to inform the system that the carrier tone from the
distant modem was being received. This signal is frequently used
by the software to display a message such as CARRIER NOT PRESENT to
help the user diagnose failure to communicate. Obviously, if the
system is designed properly to use this signal and is not connected
to a modem, the signal must be provided by a pullup resistor or
gate as described above (see Figure A-1).
Many modems expect a DTR high signal and issue a DSR response.
These signals are used by software to help prompt the operator
about possible causes of trouble. The DTR signal is sometimes used
to disconnect the phone circuit in preparation for another automatic
call. These signals are necessary in order to communicate with all
possible modems (see Figure A-1).
Sample Configurations
Figure A-1 is a good middle-of-the-road configuration that almost
always works. If the CTS and DCD signals are not received from the
modem, the jumpers can be moved to artificially provide the
needed signal.Figure A-2 shows a way of wiring an EIA-232-D connector to enable
a computer to connect to a basic terminal with only three lines. This
is feasible because most terminals have DTR and RTS signals that
are ON, and which can be used to pull up the CTS, DCD, and DSR
signals.
Two of these connectors wired back-to-back can be used. In this
implementation, however, diagnostic messages that might
otherwise be generated do not occur because all the handshaking is
bypassed. In addition, the TX and RX lines may have to be crossed
since TX from a terminal is outgoing but the TX line on a modem is
an incoming signal.Another subject to consider is the use of ground pins. There are two
pins labeled GND. Pin 7 is the SIGNAL GROUND and must be
connected to the distant device to complete the circuit. Pin 1 is the
CHASSIS GROUND, but it must be used with care. The chassis is
connected to the power ground through the green wire in the
power cord and must be connected to the chassis to be in
compliance with the electrical code.
