CHAPTER23 Digital PSTN
Mediant 800 Gateway & E-SBC | User's Manual
■ Ring Down (Ring and No Ring states): This event signals a ring or no ring state. An
example is when the user lifts the handset or pushes a button on the phone to alert the far-end
user, which instantly sends ringing to the far end (even though they are already connected).
This is also known as Automatic Ring Down (ARD) or Manual Ring Down (MRD).
■ TOS (transmission only service): If neither Ring Down or Hook Switch modes are specified
in the INVITE, TOS is assumed. In this case, the device ignores all CAS signaling, replies with
200 OK and opens a media channel.
These special private wire events are signaled during a call using the SIP INFO message in
association with the INFO package (per IETF draft). The INFO package is the INFO message's
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child elements:
■ "<ringDown>" - requests a local Ring Down alert
■ "<hookSwitch>" - requests a Hook Switch alert:
◆ "onHook" - signals that the endpoint is not in use
◆ "offHook" - signals that the endpoint is in use
The following is an example of the XML for private wire signaling in the SIP INFO message:
<?xml version="1.0" encoding="UTF-8"?>
<xsd:schema targetNamespace="urn:bt-trs:params:xml:ns:private-wire:0"
xmlns="urn:bt-trs:params:xml:ns:private-wire:0"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
elementFormDefault="qualified"
version="0.1">
<xsd:annotation>
<xsd:documentation xml:lang="en">Version 0.1 Draft XML schema
for Private Wire Signalling in SIP INFO body
</xsd:documentation>
</xsd:annotation>
<!-- pwSignal -->
<xsd:complexType name="pwSignallingType">
<xsd:sequence>
<xsd:choice>
<xsd:element ref="ringDown" />
<xsd:element ref="hookSwitch" />
<xsd:any namespace="##other" minOccurs="0"
maxOccurs="unbounded" processContents="lax" />
</xsd:choice>
</xsd:sequence>
<xsd:anyAttribute namespace="##other" processContents="lax" />
</xsd:complexType>
<xsd:element name="pwSignal" type="pwSignallingType"/>
<!-- ringDown -->
<xsd:complexType name="ringDownType">
<xsd:sequence>
<xsd:any namespace="##other" minOccurs="0"
maxOccurs="unbounded" processContents="lax" />
</xsd:sequence>
<xsd:attribute name="signal" type="ringDownSignalType" use="required"/>
<xsd:anyAttribute namespace="##other" processContents="lax" />
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