Information Technology Reference
In-Depth Information
FXS
An FXS interface is an RJ-11 connector that connects to station equipment, including phones, faxes, and modems. In contrast to FXO
interfaces, FXS interfaces provide dial tone and ring voltage.
FXS interfaces can be configured to use either loop-start or ground-start signaling. Loop-start signaling is typically used, but in the
case of a connection to a PBX or key system, ground start may be necessary.
Analog E&M
E&M can stand for Ear and Mouth, Earth and Magneto, or rEceive and transMit. E&M interfaces use an RJ-48 connector, and E&M
trunks are often used to provide tie-line connectivity for PBXs.
There are five types of E&M interfaces (types I, II, III, IV, and V), and their main characteristics are as follows:
E&M type I:
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Common in North America
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Uses E and M leads for signaling
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Does not offer ground isolation
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Cannot be used in a back-to-back configuration
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Supported on Cisco devices
E&M type II:
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Uses E, M, Signal Battery (SB), and Signal Ground (SG) leads for signaling
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Offers ground isolation
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Can be used in a back-to-back configuration
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Supported on Cisco devices
