DMG CONNECTIONS SERIAL INTEGRATION PORT

Dmg Connections Serial Integration Port

Clients of DMG Financial connect to a range of banks via Xero.To connect an analog DMG1000 Media Gateway to the serial integration port of a PBX requires some basic understanding of RS-232 wiring and hardware handshaking protocols.This document provides an overview of various serial connector pin layouts as well as some basic knowledge regarding hardware flow control configurations.This document does not discuss any PBX specific requirements nor does it attempt to educate the reader on any PBX-side configuration or wiring or connector requirements.The following technical discussion will include details covering these specific topics:Typical serial communication scenarios you will see are DTE and DCE. It is the responsibility of the contractor/applicant to be familiar with and to follow the DuPage County Wastewater Treatment Ordinance.Here at DMG Financial, we provide Taxation, Bookkeeping, Business Advisory and Cloud. Please call with any permit related questions - (630) 407-6800. DuPage County Public Works.

The cables that are typically used to connect a DTE device to a DCE device are known simply as вЂstraight throughвЂ™ cables because their design does not cross any of the signals from one end of the cable to another. In these situations the DTE is simply providing the data to the DCE to be communicated to another endpoint. Computer (DTE) connected to another Computer (DTE)Typically DTE to DCE or DCE to DTE connections do not require a communications path that crosses the transmit (Tx) and receive (Rx) wires. Modem (DCE) connected to another Modem (DCE)

In most cases, the latter device will have the fact that it is a null modem stamped somewhere on its surface as shown in the photo in figure 1.Figure 1. The purpose of the null modem is to cross transmit and receive signal paths between these like end points.Null Modems can come in several types, one being a cable that has transmit and receive wires crossed between the ends, the other being a small box-like device with a connector on each end. Devices used for these types of configurations are called вЂNull ModemsвЂ™. This will be shown in latter diagrams.Typically any DTE to DTE (or DCE to DCE) connections will require a communications path that crosses the transmit (Tx) and receive (Rx) wires.

These types of connectors are found on more modern equipment of newer design. These types of connections are typically found on equipment of older origin or design.DB-9 connectors contain 9 pins that carry the various signals that make up the RS-232 standard. Diagram showing how a Null Modem connects the Tx and Rx signals of an RS-232 interface.With respect to the type of connectors used in RS-232 systems, DTE devices typically use a male connector while DCE devices typically use a female connector.The majority of connectors used by serial devices you will encounter fall into 2 basic types, DB-25 and DB-9.DB-25 connectors contain 25 pins that carry the various signals that make up the RS-232 standard. Note that this model uses DB-25 style connectors but models that use DB-9 style connectors are also available.The primary purpose of the null modem is to, from the standpoint of one end of the connection make the opposite end appear to be a different typeFigure 2.

The intent here was that most PBX ports would be wired as DTE so making the DMG1000 Media Gateway port DCE would remove the need to use a null modem between the two devices. The port was designed as a DCE port to make it simpler to connect to a PBX. Requires no flow control pins (only uses Tx, Rx and SG)Because of this connector configuration you have to keep three key ideas in mind when performing an installation: Table showing typical pin configurations for DTE and DCE type DB-9 style serial connectors.The DB-9 serial port on the DMG1000 Media Gateway has the following properties: Table showing typical pin configurations for DTE and DCE type DB-25 style serial connectors.Figure 4. Type layouts for each type of connector and each type of serial device are shown below.Figure 3.

Some PBXs however do require handshaking signals before they will place any data on to, or accept any data from the serial link. This port will receive any data presented to it and transmit data back out to any device attached without requiring any special handshaking signals. The port was designed to not need any hardware handshaking signals. Because the DMG1000 Media Gateway uses a DB-9 style connector you may need a cable that can properly route the signals from a DB-25 connector on your PBX or serial data source to a female DB-9 connector.

Without taking any of the handshaking signals into account at this time (this will be covered latter) here is what the wiring would need to look like. This is going to require that you have a cable that is capable to passing the proper signals from the 25-pin layout across to a DB-9 type connector using the 9-pin layout. These flow control connections are discussed in the next section.One of the basic configurations you are likely to encounter in the field when connecting the DMG1000 Media Gateway to a PBX using the serial port is a condition where the PBX is using a DB-25 type connector.

This results in a connection that loops back the Data Terminal Ready (DTR) into the Data Set Ready (DSR) and Carrier Detect (CD) on the same interface. Diagram showing a RTS/CTS style of handshaking loop back connection done on a DB-25 style DTE connector.DSR/CD/DTR handshaking вЂ“ This type is achieved by connecting (on a DB-25 connector) pins 6, 8 and 20 together. The result here is that the interface thinks the far (DCE) end responded that it properly received the RTS signal and is ready to receive data.Figure 6. This resulting scenario here is that when the DTE side asserts the RTS in an attempt to signal the DCE side that it has data to send it is applying the expected acknowledgment by asserting the CTS signal back to itself. This configuration results in a connection that loops back the Request To Send (RTS) into the Clear To Send (CTS) on the same interface. Using one or the other or even both may be required depending on what your PBX interface requires.RTS/CTS handshaking вЂ“ This type is achieved by connecting (on a DB-25 connector) pins 4 and 5 together.

This device comes in many different configuration and price points depending on the features you feel that you need, but a simple model that offers you the ability to monitor signals on both sides of a serial link and then easily make the required connections is all that is needed. While you can accomplish this using just wire and several connectors the process goes much quicker using the proper tools.One indispensable tool for these situations is called a RS-232 break out box. Diagram showing a DSR/CD/DTR style of handshaking loop back connection done on a DB-25 style DTE connector.There are several other flow control loop back methods that involve various combinations of the signals shown in the above diagrams but these are two of the most common ones used.In the process of trying to determine the proper loop back configuration required for your PBX you are going to need a way to try out different combinations of signals. The results here are that the interface thinks the far (DCE) end responded that it properly received the DTR signal and is ready to send data.Figure 7.

Once a working configuration has been found that works with your system this wire configuration can then be constructed into a cable. All this testing can be done live without having to strip wire and solder connections. Photo showing a typical RS-232 break out box device.The largest advantage of using the breakout box is that it allows you to see what signals are available on each individual line of the interface and then easily create cross connections between each side of the interface to test out various loop back scenarios.