Chpt. 1 T1 Signaling Flashcards
3 characteristics of an analog signal
- frequency - speed Hz
- amplitude - size
- phase - position (degrees)
What is DDS?
Dataphone Digital Service
ATT’s digital data service.
Same as a T1 the only difference is the speed.
Slower than a T1 (2 to 56 Kbps).
What is (NCTE)?
Device that formats digital signal for compatibility with long distance networks.
(CSU/DSUs) are NCTEs.
CSUs fix BPVs?
Yes
Repeaters Fix BPVs
No
Chann. Banks support data?
Yes (DSO-A)
Repeater?
- Tx signal from origin to destination w/o errors or affect signal.
- Often cause of largest amount of problems.
Most popular types of D-Marks Connections.
- Modular
- Connectorized
- Punch Down
Diff. Between Chann. Banks and Mux.
Chann. Banks 1st T1 Mux.
24 Chann. Interface.
Encoding/Coding in / out of T1 Chann. Banks.
Analog Voice converted to DSO.
- Mux descendant of Chann. Banks (Sophisticated computer controlled bandwidth Mgr.)
- Multiplexers are mainly used to increase the amount of data that can be sent over the network within a certain amount of time and bandwidth.
- A multiplexer is also called a data selector.
- Multiple-input, single-output switch, and a demultiplexer as a single-input, multiple-output switch.
(CSU)
Chann. Service Unit
Network protection FCC part 68.
Test access point.
DACS?
Digital Access Cross Connects.
(Grooming/Like Destinations)
Grooming
Circuits from various locations are combined for traffic going to “like” destinations.
When are A bits transmitted?
6th Frame of the bit stream.
Diff between Framing / Formatting
Framing determines “when/where” a Chann. Is in the bit stream.
Formatting is how user bandwidth is divided/compatible at the end points of a network.
(CRC)
Cyclic Redundancy Checking
Error checking.
More accurate than BPV.
Checks Logic Errors too.
Phase?
Position of analog signal in degrees.
A/D Conversation?
Creates 1st step in T1 = (PCM)
Pulse Code Modulation.
(PCM) digital voices encoded content of a VF Chann. Generated by a modem.
Takes a signal from an analog sinewave to digital binary pulses to be compatible on a data network.
Purpose of Framing?
Allows device to know “when/where” a Chann. is in a digital bit stream.
Must know what bit is next / how many have passed.
How many Frames make up a “SuperFrame”
12
DSI Frame holds how many Chann.
24
How many Chann. Are in a “Standard T1 Format?
24
Main diff. Between “SF / ESF”
“SF” 12 Frames for voice signaling/Uses Data lines to detect errors and no maintenance Chann. for testing.
“ESF” has (CRC) for error checking and secondary Maintenence Chann. so testing does not disrupt all circuits.
Fractional T1 does not Require Synchronization?
False.
Why is Synchronization an issue?
Locks all network clocks in phase/freq.
Accuracy/Stability are grouped together that’s “Synchronization”.
Locks all network clocks in Phase / Freq. to common network Freq.
Stability?
Clock Never Changes
A clocks performance with no other clock source.
Free running
Same time never changes.
