> For the complete documentation index, see [llms.txt](https://gsm.learn-telecom.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://gsm.learn-telecom.com/gsm-interfaces/a-interface.md).

# A interface

A interface connects a MSC and BSC Transcoder.

As data from User and Signaling

64 kbps per time slot

128 channels

Adaptation from ISDN-S2M interface, the interface can handle up to 8192 kbps of data. 

This interface is crucial for ensuring efficient communication and data transfer between the MSC and BSC Transcoder, maintaining the integrity of both user data and signaling information. 

The adaptation from the ISDN-S2M interface ensures compatibility and streamlined operations within the cellular network infrastructure.

#### Understanding the ISDN-S2M Interface in Cellular Networks

The ISDN-S2M interface is essential for seamless integration within cellular networks, connecting the Mobile Switching Center (MSC) and the Base Station Controller (BSC) Transcoder. 

* **Data Handling:** The interface supports high-speed data transfer at rates up to 8192 kbps.
* **Channel Capacity:** It utilizes 128 channels, with each time slot capable of transmitting at 64 kbps.
* **Purpose:** This ensures that both user data and signaling information are transmitted effectively, maintaining data integrity across the network infrastructure.