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is the most common type of telephony signaling used in today's corporate and service provider networks.
a bit is "robbed" from designated frames to use for signaling purposes.
robbed bit signaling
inserts the signaling information into the digital voice stream without affecting voice quality.
robbed bit signaling
what type of current is needed to signal the end switch or office
Direct Current (DC)
indicates transition state changes by toggling on or off the flow
Simple form of DC signaling between the subscriber and the local end office
"there is no flow"
used on trunking lines or tie-lines
recEive and transMit (E&M) ground(earth) and voltage (magneto)
what is the problem with dc signaling
- limited to the number of states
- When you use the same pair of wires for voice and signaling, the lines or trunks are kept busy even when the two subscribers are not connected.
Uses tones in place of DC
in band signaling
three inband frequency
- Single Frequency,
- Multi-Frequency (MF)
- Dual-Tone Multi-Frequency (DTMF)
This tone is used for interoffice trunks and has two possible states:
On-hook or idle,
off-hook or busy.
Single frequency tone
features of single frequency tone
- frequency of 2600Hz
- No tone is present when a connection or circuit is up.
- When either party hangs up, however, a 2600 Hz tone is sent over the circuit, notifying all interoffice exchanges of the disconnect.
what is MF multi frequency
- This tone is used by interoffice trunks to indicate events, such as seizure, release, answer, and acknowledge, and to transmit information,such as the calling party number.
- uses a combination of pulses specified by frequencies to signal across a network.
- less efficient
what is DTMF "Dual-Tone Multi-Frequency"
- to transmit telephone number digits from the subscriber to the local office.
- subscriber presses one of these keys, the oscillator sends two simultaneous tones
DTMF tones identify
the numbers 0 through 9 the "*" and "#" up to 16 combination exits
what is Loop-Start Signaling
- •The most common form of subscriber loop signaling. •The creation of a loop initiates a call and the closure of a loop terminates a call.
- •The simplest and least intelligent of the two signaling protocols.
draw back to loop start signaling
what is ground signaling
- Current-detection mechanisms are used at each end of the trunk, enabling end office switches to agree on which end is seizing the trunk before it is seized.
- Minimizes the effect of glare and costs the same as loop-start signaling.
- The preferred signaling method for PBXs.
carry signaling information from the trunk in the trunk itself
Channel Associated Signaling (CAS)
Uses a common link to carry signaling information for a number of trunks. Cheaper, has faster connect times, and is more flexible than CAS.
Common Channel Signaling (CCS)
what is the second generation of CCS
common trunk-signaling technique used on telephony switches and PBXs
The signaling and voice trunks in E&M are
Voice is transmitted over what type of circits and how many methods for signaling
that operate over various analog and digital facilities.
analog facilities are either two- or four-wire
T1 North America
CAS Channel Associated Signaling
signaling is compatible with SS7
also enables PBXs to connect over the PSTN and create VPNs
Includes two access methods: Basic Rate Interface (BRI) and Primary Rate Interface (PRI). (Used for small companies 23 or fewer callers )
Speech, 3.1 kHz audio (for modem data), and 64 kbps digital data
These services also are typically found on PBXs and virtual private voice networks
services:calling line identification (caller ID), closed users groups, call waiting, user-to-user signaling, advice of charge, call forward, and call hold.
typically found on PBXs and virtual private voice networks.
is a 64 kbps channel that carries user information streams.
No signaling information is carried
user streams include
speech encoded at 64 kbps according to ITU G.711
B Channel ( data)
channel is used primarily to carry signaling for circuit switching by ISDN networks
bit rates are different depending on the access method.
is capable of transmitting user packet data up to 9.6 kbps.
D Channel (signaling)
Two types of access methods exist for ISDN:
two bi-directional 64 kbps B channels and one bi-directional 16 kbps D channel over standard two-wire telephone lines.
Used in SOHO
Each B channel cantransmit speech or data;
the D channel transmits the signaling or call control messages
Corresponds to two primary rates: 1.544 Mbps (T1) and 2.048 Mbps (E1).
The interface structure for T1 is 23B + one 64 kbps D
Typically are used in medium to large business applications.
ISDN user-network interface L2 and L3 specifications
Digital Subscriber Signaling System No. 1 (DSS1).
protocol provides the reliable transfer of frames between the local exchange and the TE.
also secure connections
mechanism for call establishment, control, and access to services.
a peer-to-peer signaling system used in corporate voice networking for inter-PBX communications
It is a standards-based protocol enabling the interconnection of multivendor equipment.
Generic Functional Procedures (QSIG GF)
Architecture and Reference Points
Basic Call Setup and Teardown
Key aspects of QSIG
Basic service (QSIG BC)- setup manageand tear down
QSIG GF- standardized method for transporting nonstandard features
Supplementary services- caller id call forwarding
QSIG has an identical structure to that of ISDN, and at layers
What layer do QSIG differ
the interfaces and messages for the user and network sides are identical.
Symmetrical protocol (QSIG BC)
Specifies the control entities for supplementary services and ANFs.