REALIZING THE TELEGRAPH SIGNALING ON PORTS WITH RS232

Abstract

One of the basic issues, arising at modernizing the switching equipment of telegraph networks Telex/AT50 is studied. The question concerns the choice of the method of building ports and the implementation of telegraph signaling at the port of telegraph switching equipment. The purpose of the development is creating equipment that will ensure the smooth integration of telegraph users in data networks. The implementation of a port built on the basis of Universal controller of asynchronous transceiver with the RS- 232 interface type 16550 is considered.The use of the controller in modern computing systems and the associated data transfer procedures are presented. The characteristic features of the controller are described. The telegraph signaling procedures used to establish a connection through the Telex/AT50 network, exchange data and then terminate the connection are considered. The issues of interoperability standard universal asynchronous receiver-transmitter with an interface of the RS 232 type 16550 with the procedures of establishing/breaking connections adopted in switched telegraph networks Telex/AT50 are analyzed. The conclusion on the incompatibility of the controller with the telegraph signaling regarding the procedures for establishing/disconnecting the connection is substantiated, the occurring negative phenomena are considered and their main cause is described. One of the methods of implementing a telegraph interface with switched telegraph channels, which is more functional than other approaches, is presented. It is described how to overcome the incompatibility based on the use of an external modem telegraph having additional functional manageable inversion signal strength at reception and transmission. The implementation schemes of realizing separate control on the directions, using RS 232 are considered. Examples of implementation of individual procedures at the stages of establishing and disconnecting of the telegraph connection, as well as the implementation of specific dialing procedures, using the pulse method are given. A functional block diagram of the interface with the telegraph channel implemented on the basis of a 16550 type  controller is presented.