|
A T1 is considered to be a partial T1 when it carries circuits that add up to something less than the capacity of the T1. For example, since a T1 runs at 1.544Mhz, it is capable of carrying any circuit (or combination of circuits) running at speeds up to its own speed of 1.536Mhz (8kb is required for T1 framing and line coding). Applications that require a 256kb circuit or a 512kb circuit would require less than a full T1 for access. A partial T1 line can best be described as having available bandwidth leftover, after all current services have been provisioned. In some cases, a partial T1s can also be considered a fractional T1s, when the T1 carries data services running at greater than DS0 speeds, and also has unused bandwidth. The key differences between the two are that partial T1s, by definition, only have available bandwidth remaining, and can carry a combination of voice, data, or both in an Integrated T1 configuration. Fractional T1s, by definition, could be fully loaded, but must carry at least one service running at greater than 64kb (DS0) speed. Typical Examples:
ESF/B8ZS T1s also have the benefit of ESF monitoring, which allows the carrier to setup ESFMUs (monitoring units) to watch the performance of the T1 itself without disrupting the services carried by the T1. ESFMUs track performance using the 8kb ESF channel for statistics. ESF/B8ZS is required for Fractional T1s since the access T1 is not channelized, and contiguous bandwidth is required to allow a single circuit greater than DS0 speed. Termination Options. Partial T1s will typically terminate at the customer premises into a variety of options, including a channel bank, DTI Card (Direct Termination Interface to a PBX), D/I Mux, or TDM Mux. (Note: if these devices don't provide CSU-functionality, the T1 will terminate first into a CSU for testing and line build-out equalization, then into the device) The CPE termination equipment (Customer Premises Equipment) will be dependant upon the services carried by the T1.
 
Other Termination Options. Partial T1s may be combined with other T1s on a DS3 access facility. If this is the case, the T1 that is partial will typically be de-multiplexed (from the access DS3) at the customer facility using an M13. Once at the T1 level, a D/I mux or TDM mux may be used. |
Partial T1
