PTSN communications program

First, the program plans

In this scenario, all TPC using Modem to connect to the telephone network, the server also uses Modem connected to the telephone network.

Second, the program narrative

There are several changes in the program form.
1、TPC single permanent connection
In this way, the server using a Modem to connect to through the telephone network on a TPC. Dial-up server to the TPC from TPC to the server or dial-up can be. MCGS after connection disconnected automatically re-dial-up connections to maintain. This approach can guarantee the use of 1 ~ 3 seconds PC refresh the data. Sync up the most historical data.
2、TPC multiple permanent connection
In this way, the server on each TPC using a Modem and a telephone line, to maintain the connection of each TPC. Refresh data in this way is faster. However, due to operating costs of this approach is relatively high, rarely used. Internal telephone network for the units, consider using this approach.
3、Single / multiple TPC from time to time to connect
In this way, the server only a Modem and a telephone line. TPC from time to time transmission of data in various dial. In this way, the often-time real-time data transmission, as well as a small amount of historical data, reports, data, alarm data and so on. Dial operation from time to time by the host computer is usually responsible for initiating. A small number of cases initiated by the TPC-side, but this will easily lead to multiple collisions TPC at the same time dial-up.
4、Single / multiple TPC-on-demand connection
In this way, through a script control, end-users based on their needs, command dial PC system to obtain real-time data to a TPC. In this way and the third approach is usually used in combination to meet the user's tasks and regularly collected both on-demand needs.
5、TPC initiative to send a dial-up data on
In this way, it is necessary configuration in the TPC in the strategy, after the occurrence of certain things, automatic dial-up connection server, to send real-time data and historical data, alarm data. Transmission is completed, automatically hang up. In this way, and 3,4 are often used in two ways. Dial-up trigger events may be from time to time they can also be triggered by the alarm.