ATT System 25 Reference Manual

FUNCTIONAL DESCRIPTION
DATA TERMINAL
EQUIPMENT,RS-232C
HOST C0MPUTER
SINGLE-LINEVOICE TERMINAL
Z3A1/2/4ADU
(2500-SERIES
7101A OR 7102A)
DATA TERMINAL
EQUIPMENT,RS-232CTN726DATA LINE CPHOST COMPUTERZ3A5ADU
MULTILINEVOICE TERMINAL
(7300H-TYPE)
ATL CORDEDAND CORDLESS
TELEPHONES
CO, FX, WATS______
PAGING
EQUIPMENT
DID TRUNKS
TIE TRUNKS
T1 CARRIER
PART OF DIGITAL SWITCH
TN726DATA LINE CP
TN724
ANALOG LINE
CP ORZTN78 TIP
RING LINE CP
ZTN79
ATL LINE CP
ZTN76
GROUND STARTTRUNK CPOR
ZTN77LOOP START
TRUNK CP...

FUNCTIONAL DESCRIPTION
SAT, DTU, SMDR,
CAS (ON-PREMISES)
(DIRECT CONNECTION)
Z3A1ADU*Z3A4
ADU
*
* REQUIRED FOR CONNECTIONS >50 FEET
OR NOT SHARING SAME AC OUTLET
SAT, SMDR,CAS (ON-PREMISESSWITCHED CONNECTION)
Z3A1/4ADU
Z3A4ADU
TN726
DATA LINE CP
SAT, SMDR,CAS (OFF-PREMISES
DIRECT CONNECTION)
MODEM(212-TYPE)COMODEM(212-TYPE)
SAT, SMDR,CASE (OFF-PREMISESSWITCHED CONNECTION)†OPSTN742
ANALOG LINE CP
MODEM(212-TYPE)COOR
CO
† OFF-PREMISES STATION
OR CO TRUNK
Z3A4ADU
PART OF DIGITAL SWITCH
ZTN142
CPU/MEM CP(1)...

FUNCTIONAL DESCRIPTION
SINGLE-LINE VOICE TERMINALS
(42, 500, 2500-SERIES, 7101A,
7102A)
——————————
RECORDED ANNOUNCEMENTS
——————————
DICTATION EQUIPMENT
——————————
EXTERNAL ALERTING DEVICES
——————————
MUSIC-ON-HOLD
MULTILINE TERMINALS
(7300H-TYPE
——————————DIRECT TRUNK ATTENDANT
CONSOLE OR SWITCHED LOOP
ATTENDANT CONSOLE
——————————ATTENDANT DIRECT EXTENSION
SELECTOR CONSOLE
(MODEL 23A1)
——————————ATL CORDED AND CORDLESS
TELEPHONES
MET SETS
DICTATION EQUIPMENT——————————
PAGING EQUIPMENT
(PagePac)
NETWORK...

FUNCTIONAL DESCRIPTION
The SAKI also does the following functions:
—
—
—
—
—
—
—
Identifies the circuit pack to the Common Control (location and vintage)
Controls status indicator Light-Emitting Diodes (LEDs) — red (failure), green
(translated), and yellow (circuit busy)
Initiates power-on startup procedures
Checks the on-board microprocessor for sanity and causes reinitialization in
case of problems
Takes NPEs out of service under control of the on-board microprocessor
Resets the protocol handler on the...

FUNCTIONAL DESCRIPTION
l NPE (Network Processing Element)
Each port circuit pack contains one or two NPEs. The Analog Line, ATL Line, Tip
Ring, Data Line, Ground Start, Loop Start, and DID Trunk Circuit Packs contain two
NPEs. The MET Line, Auxiliary Trunk, and Tie Trunk Circuit Packs contain one NPE.
The NPEs do switching network functions for the port circuits. Under control of the
on-board microprocessor, an NPE can connect a port circuit to any one of the TDM
bus time slots. More specifically, it...

FUNCTIONAL DESCRIPTION
Figure 3-7. Analog Line (TN742) Unique Circuitry
l Port Circuits
The eight port circuits are identical. Each port circuit consists of a coder/decoder (codec),
hybrid circuit, electronic battery feed circuit, ring relay, and overvoltage surge protection
circuit.
The codec is a 4-wire circuit that converts the analog signal from a voice terminal to a PCM
data signal. It converts an incoming PCM data signal from the NPEs to an analog signal.
The hybrid circuit converts the 4-wire...

FUNCTIONAL DESCRIPTION
The electronic battery feed circuit provides talking battery to the voice terminal. It also
produces a controlled dc battery feed for short and long loops, detects when a receiver is
lifted, and provides the message waiting signal by periodically turning off the feed voltage.
The ring relay provides the interface between the ringing application circuit and the port
circuit. It causes ringing turn on and turn off.
The overvoltage surge protection circuit provides lightning surge and...

FUNCTIONAL DESCRIPTION
TOMULTILINEVOICETERMINALSAND
ATL
CORDED
AND
CORDLESS
TELEPHONES
Figure 3-8.ATL Line (ZTN79) Unique Circuitry
3-17 

FUNCTIONAL DESCRIPTION
Auxiliary Trunk (TN763)
The Auxiliary Trunk Circuit Pack (Figure 3-9) interfaces four ports provided for customer-
provided equipment (CPE) and the TDM bus.It is connected to the CPE by up to three pairs
of wires. The transmission pair (T and R) carry voice signals and touch-tone control signals.
The T and R also provide a loop start seizure indication to the CPE. The seizure pair (SZ
and SZ1) provide seizure indication to the CPE. The signal pair (S and S1) provide answer...

FUNCTIONAL DESCRIPTION
ON-BOARD
MICROPROCESSOR
TOAUXILIARY
EQUIPMENT
Figure 3-9.Auxiliary Trunk (TN763) Unique Circuitry
Data Line (TN726)
The Data Line Circuit Pack (Figure 3-10) interfaces eight Asynchronous Data Units (ADUs)
data devices and the TDM bus. The ADUs are typically, in turn, connected to RS-232 type
devices. The Data Line has the following unique circuitry:
l Bit Clock
The bit clock circuitry is used to provide the Octal Asynchronous Terminal Mode Two
EIA Asynchronous LSIs (OATMEALs) with...