Multiple Low Speed Data Transmission / Polling

Problem
You have a traffic control system which monitors traffic flow throughout a large urban area. Each of the major roads has several data collection locations. Each location uses only a fractional portion of the T1 stream. Your collection devices have an RS-232C interface and run at a speed of 4.8 Kbps. How can you efficiently collect your data and send it along the T1 to other locations?

Solution
Coastcom's five port pSDMs allow you to gather data from multiple low speed circuits and efficiently multiplex them onto one transmission channel (DS0). Using polling as a method of contacting sites and accepting data from them, you can share transmission channels. Coastcom's D/I Mux III then takes the DS0 and multiplexes it onto a T1.

How Does It Work?
A polling device at the hub individually addresses each pSDM. When addressed the pSDM sends information back over the T1 to the polling device. This method allows multiple sites to share a transmission channel and saves precious bandwidth.

Figure d14. Multiple Low Speed Data Transmission/Polling

What Actually Occurs?
Hank and William are traffic control monitors. Their job is to watch the flow of commute traffic and to deal with snarls and congestion when they occur. Their job is made easier with the new traffic monitoring and control systems that have been installed in their community.

D/I Mux IIIs are set up in a drop and insert string throughout the area. Transmission channels are dropped off to monitor various road conditions at each site. Information from the various sites includes the amount of traffic, the speed of traffic, and even conditions at the monitoring station, such as fire alarms, equipment failure, etc.

Hank and William use a view screen with a graphical interface and page through major problem areas on a regular basis. A computer polls each site in a round robin fashion and requests data. The site sends data only when it is asked. By using a method of polling the network can be configured to monitor an extremely large system of highways, stringing together new sites as needed.

The diagram shows a small fraction of one drop and insert string. Each site in the diagram can share the same transmission channel and only reports back when it is asked. The pSDM has five sub channels available. Each sub channel can be connected to a different device and be set for a different data rate. An alarm circuit may only require a 2.4 Kbps data rate, while a traffic counter may require 19.2 Kbps. Both data rates can be accommodated in the same card.

How Do You Set It Up?
Set the five subrate channels in the pSDM for the appropriate data rates. Set the pSDM for polling operation.

What Do You Order?
The pSDM supports up to five circuits of 9.6, 4.8, or 2.4 Kbps data or two at 19.2 Kbps plus one at a lower speed. pSDM cards require I/O panels in order to access the five separate channels. Therefore, if you have five 4.8 Kbps circuits going from one point to another you would need a pSDM card, an I/O panel, and a D/I Mux III at each end.

Video Conference Room

Problem
Golden Pelican publishing has offices in Nashville and Los Angeles. Their management team has decided to look at video conferences as an alternative to flying its managers and clients between the two offices. You are the communications manager and have a T1 network in place to carry voice and data between the two sites.

Solution
A SDCU with a video CODEC will allow you to create a video conference over your existing T1 lines.

How Does It Work?
A SDCU installed in a D/I Mux III offers a high speed data line to carry a compressed video signal. The SDCU offers data rates of 56/64 x N Kbps where N is the number of transmission channels used, up to 24. The T1 lines are private leased lines so the T1 carrier does not need to be notified of changes in the network.

Figure d15. Video Conference Room

What Actually Occurs?
Loran Sands, the artist and repertory person for Golden Pelican music, has discovered a new songwriter, Rose Sebastian, who writes sultry blues in the style of Golden Pelican artist Malvern Hill. Malvern has heard one of the songs and wants to record it. Rose is looking to establish her own career as a singer and wants to retain the rights to perform her own music.

Loran Sands sets up a video conference call with both artists. From the video conference room the video signal leaves the CODEC in a standard data interface (V.35) and enters the SDCU. The SDCU and D/I Mux III then transport the signal over T1. At the Nashville video conference room the T1 signal enters the D/I Mux III. The SDCU then supplies the CODEC with the V.35 data interface it requires.

When the conference is completed the D/I Mux III can be reprogrammed to allow the video conference channels to be used for other purposes.

How Do You Set It Up?
Place an SDCU into a channel card slot of each D/I Mux III. Connect the SDCUs to the Video Conference CODECs. Configure both SDCUs for a data rate which is compatible with the Video Conference CODECs.

What Do You Order?
Two SDCUs and two D/I Mux III systems are required. If you have an existing system with available bandwidth only the SDCUs would be required. Coastcom offers a choice of 56/64 x N Kbps SDCUs with either a V.35 or RS-449/422 interface. A D/I Mux III is required at each site. Coastcom also has more economical SDCUs that offer 56 Kbps or 64 Kbps data. The video conference CODECs would be purchased from another vendor.

Fractional T1 Concentrator

Problem
You have multiple sites each using a fraction of a T1. A hub sitehub site has been selected into which you bring each fractional T1. You want to combine the fractional T1s into a full T1 and transport the lot across the country. In the past your alternative would have been to either convert the fractional T1s to another protocol or concentrate them into a T1 with expensive DCS equipment.

Solution
Coastcom's TTU plug in channel card can save you the expense of DCS equipment or protocol conversions at your hub site, while still offering you the full functionality of T1.

How Does It Work?
Several TTUs are placed into a D/I Mux III channel bank. The D/I Mux III takes the fractional T1 and multiplexes it into a full T1.

Figure d16. Fractional T1 Concentrator

What Actually Occurs?
Dos Costas Inc. is a large scale waste management company with operations on both the Atlantic and the Pacific Coast. Their regional headquarters are located in Wilmington, Delaware and in Fresno, California.

The Fresno site is spread out in a campus environment. There are several different salvage and recycling functions going on at any one time. Between buildings they have copper T1s to handle communications and keep track of inventory.

They found that by combining the fractional T1s into a single T1 for cross country transmission they can cut costs.

The fractional T1s coming into the hub site are each terminated into a TTU. D/I Mux III multiplexes the channels in the TTU into a full T1 transmission channel. The T1 is then sent across the country to Delaware.

In Delaware, the T1 is terminated into another D/I Mux III and the data is downloaded onto a computer system for processing and storage.

How Do You Set It Up?
The TTUs are set up to accept from 1 to 24 DS0s as needed. In the D/I Mux III the TTU is programmed to the required number of DS0s. Set the TTU and the remote D/I Mux III to the same framing formats and line formats. Set the remote D/I Mux III to loop timing so that it can recover clock from the TTU. Set the TTU to accept clock from the PSN's incoming T1.

What Do You Order?
You will require one TTU for every fractional T1 termination. For example if you have four fractional T1s, each using 256 Kbps, you will require four TTUs and one D/I Mux III.