DATA SERVICES OVERVIEW
System 25’s data features provide switched data transmission at up to 19,200 bps
The system provides switched connections between data endpoints. These endpoints include data terminals, personal computers, multiport computers, and modems. Data endpoints are either digital data endpoints or analog data endpoints.
Analog endpoints are connected to System 25 voice terminal or trunk port circuits through a modem in the traditional manner. Digital endpoints are connected to System 25 data port circuits on the TN726 Data Line CP. A data module (specifically, an Asynchronous Data Unit - ADU) is required in place of the modem used with analog endpoints. Section 4 of this manual shows the connections supported and required connecting equipment.
Data C alls can be set up between data endpoints. Analog to analog and digital to digital connections are straightforward; calls between analog and digital endpoints are possible only if the system is equipped with a conversion resource (TN758 Pooled Modem Circuit Pack or external modem pool). System 25 data calls from analog endpoints (including those to digital endpoints) are set up in the traditional manner. The calling party should follow the procedures supplied with his/her modem. However, a Modem Request Code must be dialed when calling a digital endpoint.
Call
In the discussion that follows, it is important to understand the difference between analog voice terminology and data terminology. Refer to the “Glossary” (Section 9).
The following provides a definition of a data call in terms of its contextual components. The components are (1) data endpoints, (2) data endpoint states, (3) data call processing modes,
(4) connecting configurations, and (5) controlling features.
Data Endpoints |
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Data endpoints are composed of data | equipment, | a data module or modem, and | a connection | |
to the switch via an analog or data | port. A digital data endpoint is addressed | by its | Data | |
Dial Code (DDC). Analog data endpoints are addressed like other voice terminals, by | their | |||
PDCs. For the remainder of this description, | data endpoints will refer to | digital | data | |
endpoints unless stated otherwise. |
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Several different categories of data endpoints are supported. The categories have been divided into two general groups, those having a DTE type interface, which encompasses almost all of the data terminal devices, and a group of DCE interface devices (primarily modems ). The groups have then been divided into categories based upon their functional attributes. However, it must be noted that within each category, control interfaces may vary. The following describes the categories and attributes of each:
1.DTE Devices
T h i s g r o u p o f d a t a e n d p o i n t s h a v e o n e t h i n g i n c o m m o n : t h e i r i n t e r f a c e configuration (although
