atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services T1's, CSU's and DSU's Fractional t-1

Could anyone please tell me how to fraction a point to point t-1. I need to connect 2 phone systems together using this configuration. Is it as simple as connecting 2 csu/dsu's on each end?

???
Do you have fractional from the telco/provider or do you have the full bandwidth and need to allocate it yourself?

Also, this should be better if it was in the T1 forum?

What are you trying to do? Allocate some of the bandwidth for voice and some for data?

We used to use Channel Banks for that sort of application. Simple, straightforward, direct.

Sam

Drop and Insert boxes work great. Most CSU manufacturers make them. Look at Adtran CSU/DSU combo.

Fractional T1 (FT1) are essentially a superate digital data circuit. Where a conventional DDS circuit data rate can be up to 64Kb/s (One DS0 channel), a FT1 is comprised of multiple and contiguous DS0 channels that are assigned to an access T1.

For example, a 384Kb/s FT1 consists of six 64Kb/s DS0 channels. The 384Kb/s bandwidth is assigned to a T1 that terminates at the end user locations. Typically two access T1's unless you are dealing with a LD telephone service provider, or Internet ISP.

The 384Kb/s is carried by the access T1 from the customer location to the serving co of with whom the FT1 was contracted with.

The FT1 channel is groomed off the access T1 at a 1/0 Digital Cross-connect System (AKA: DACS), where the bandwidth is now carried over the service provides network at the actual FT1 data rate. In the example given, at 384Kb/s.

Some service providers might build a point to point T1 between two locations, and block the unused channels not paid for. Highly unlikely these days because of bandwidth constraints, and represents an old way of doing business.

Keep in mind, sending a frame bit error, such as during pre-tests will not be received at the other end if the FT1 is routed & groomed at a 1/0 DACS frame.

FT1's groomed at a DACS will always have network timing at both FT1 ends.

The situation may change depending on who the FT1 is being engineered to. But essentially the above mentioned is how these circuits work.


Field Ops

Follow up to your question regarding connecting two phone systems over a FT1. In Verizon East (Former Bell Atlantic) FT1's are treated as pure digital data (DDS) circuits.

The FT1 DS0's groomed at a DACS are not capable of carrying DS0 robbed bit signaling within each channel pair cross-connect. The robbed bit signaling option is either TRANSPARENT MUX (TRSP, MUX), or just plain old TRANSPARENT (TRSP).

Even if you were to use a D type channel bank at each end, without robbed bit signaling capability in the FT1 you will not be able to signal across the link unless you use in-band signaling or VoIP.

Field Ops