PULSECOM 4TOLB-3L1 User manual

Practice Section 1306
Issue 2, May 1992
1
Figure 1. 4TOLB-3L1 Channel Unit
with Loopback
Pulsecom
T
E
S
T
4TOLB-3L1
LB
®
D105177-1
REV A
ON
OFF
MAN
1. INTRODUCTION
This practice describes the Pulsecom
®
4TOLB-3L1 4-Wire, 600-Ohm Transmission Only
Channel Unit with Loopback, shown in Figure 1. Installation instructions and engineering
references are included.
Trademarks used in this manual:
CLEI is a trademark of Bellcore.
Pulsecom is a registered trademark of Hubbell Inc.
SLC is a registered trademark of AT&T.
The Recognized Component Mark is a registered trademark of Underwriters Laboratories Inc.
©1992 Pulse Communications Inc.All rights reserved.
CONTENTS PAGE
1. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . 1
A. Reason for Reissue . . . . . . . . . . . . . . . . . . 2
B. Features . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. APPLICATIONS . . . . . . . . . . . . . . . . . . . . . . . . 3
3. INSTALLATION AND ALIGNMENT . . . . . . . . . 4
A. Options. . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
B. Connections . . . . . . . . . . . . . . . . . . . . . . . . 7
C. Adjustments . . . . . . . . . . . . . . . . . . . . . . . . 7
4. CIRCUIT DESCRIPTION . . . . . . . . . . . . . . . . 11
A. VF Transmit Operation. . . . . . . . . . . . . . . 11
B. VF Receive Operation . . . . . . . . . . . . . . . 16
C. Loopback Circuit. . . . . . . . . . . . . . . . . . . . 16
5. SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . 17
6. MAINTENANCE . . . . . . . . . . . . . . . . . . . . . . . 17
7. CUSTOMER SERVICE. . . . . . . . . . . . . . . . . . 20
D4 CARRIER SYSTEM
4TOLB-3L1 4-WIRE, 600-OHM TRANSMISSION ONLY
CHANNEL UNIT WITH LOOPBACK
UL RECOGNIZED TELEPHONE EQUIPMENT
CLEI™ Code D4C0P885AA

4TOLB-3L1
1306, Issue 2, May 1992
2
A. Reason for Reissue
Document Reissue
This practice has been reissued to change the power specifications in Table 3 and to add
UL recognition.
Equipment Reissue
The 4TOLB-3L1 differs from the Pulsecom 4TOLB, 4TOLB-2, and 4TOLB-1L3 channel
units as shown in Table 1. The 4TOLB-3L1 also provides sealing current with single
switch selection of source/sink/off and improved current regulation over loop length in the
source mode. A –40 ° C to +85 ° C functional temperature range and switch selection of
loopback card-edge connector assignments allow use of the 4TOLB-3L1 in SLC
®
96
applications. The four units function the same in all other respects.
Table 1. 4TOLB Equipment Differences
A. LBTone,TRMT ATTN, and LB Gain
Model LB Tone Total Transmit Attenuation Loopback Gain
4TOLB-3L1 2713 Hz 32.5 dB ± 31.75 dB
4TOLB-1L3* 2713 Hz 31.75 dB 0,8,16 dB
4TOLB* 2713 Hz 24.0 dB 0,8,16 dB
4TOLB-2* 2400 Hz 24.0 dB 0,8,16 dB
B. TEK5/TEK6 and LB Lead Functions
Model
Lead Functions and Connector Pins
TEK5 TEK6 Local LB Local LB GND
4TOLB-3L1
a) D4/SLC 96 COT
b) SLC 96 RT 46 52 48 49 45 25 19 23
4TOLB-1L3*,
4TOLB*, and
4TOLB-2*
45 46 48 19
*Manufacture discontinued.

3
4TOLB-3L1
1306, Issue 2, May 1992
B. Features
The channel unit provides the following functional features:
•
4-wire voice-frequency (VF) transmission with DC isolation
•
Attenuation in the transmit (TRMT) and receive (RCV) paths selected with DIP
switches to compensate for variations in transmission levels
•
Front-panel maintenance-access connector (MAC) with bifurcated contacts
•
Loopback (LB) circuit with three-way LB activation: local, manual, or tone
•
Sealing current source/sink available with power-up ZAP (source mode)
•
Loopback gain/loss selectable from 0 to 31.75 dB in 0.25-dB steps
•
Can be used in the Pulsecom PD4 or PSC-96 channel bank
•
Can be used in the AT&T D4 or SLC 96 channel bank
•
Conductive front panel grounded to the frame
•
UL recognized
2. APPLICATIONS
The channel unit provides a 4-wire 600-ohm interface between a D4 or SLC 96 channel
bank and a 4-wire VF transmission facility with no DC signaling.An active loopback
circuit with an LB tone frequency of 2713 Hz is included. The LB circuit allows remote or
local testing of the 4-wire facility.
The unit can also be used on tandem carrier circuits utilizing end-to-end single-frequency
(SF) signaling. Figure 2 shows a typical application.
Figure 2. 4TOLB-3L1 Typical Application
T1
R1
T
R
DATA
STATION
TERMINATION
LB
X
F
M
R
RCV
ATTN
X
F
M
R
X
F
M
R
TRMT
ATTN
X
F
M
R
LB
G/L
LB
RELAY
LB
4TOLB-3L1
D4 CHANNEL BANK
T1
R1
T
R
DATA
STATION
TERMINATION
OFFICE A
D4
CHANNEL
BANK
OFFICE B
4ETO
T1
LINES
(1.544
MHz)
CUSTOMER
SITE

4TOLB-3L1
1306, Issue 2, May 1992
4
3. INSTALLATION AND ALIGNMENT
WARNING
This unit includes components that are susceptible to damage from static
electricity. DO NOT handle units without protection from electrostatic
discharge (ESD).
CAUTION
1. When replacing older 4TOLB units, reconnect loopback function leads
on the backplane. See Table 1.
2. Use a 325A power converter unit if a 48-channel bank is to be filled
with 4TOLB-3L1 plugs.The standard power module may not be able to
supply sufficient +12V power.
A. Options
General
The following options provided by the unit allow flexibility of application. These options
are selected by setting switches on the pc board and front panel. Switch locations are
shown in Figure 3. Detailed information for switch selection is given in Table 2.
Figure 3. 4TOLB-3L1 Switch Locations
.1 .2 .4 .8 1 2 4 8 16
TRMT ATTN S2S1
IN
.25 .5 1 2 4 8 16 G
IN
GAIN (G) / LOSS (L)
S8
S7
.1 .2 .4 .8 1.5 3 6 12
IN
RCV ATTN S3S4
S6
RT
D4/COT
SEALING CURRENT
S5
SINK SRCOFF
IN
S9
20 MIN TONE
4
NOTE: UNITS ARE SHIPPED WITH ALL ATTENUATION SWITCHES SET TO THE IN POSITION.
L

5
4TOLB-3L1
1306, Issue 2, May 1992
Table 2. 4TOLB Switch Options
Option Switch Designation (Note 1) S1 S2 S3 S4 S5 S6 S7 S8 S9
Name Function .1 .2 .4 .8 1 2 4 8 16 12 6 3 1.5 .8 .4 .2 .1
OFF SINK SRC D4/COT
RT .25 .5 1 2 4 8 16
G/L TONE 4/20 MIN
Transmit
Attenuation
(Note 2)
0.1 dB I O O O O O O O O
0.2 dB O I O O O O O O O
0.4 dB O O I O O O O O O
0.8 dB O O O I O O O O O
1.0 dB O O O O I O O O O
2.0 dB O O O O O I O O O
4.0 dB O O O O O O I O O
8.0 dB O O O O O O O I O
16.0 dB O O O O O O O O I
Receive
Attenuation
(Note 2)
12.0 dB I O O O O O O O
6.0 dB O I O O O O O O
3.0 dB O O I O O O O O
1.5 dB O O O I O O O O
0.8 dB O O O O I O O O
0.4 dB O O O O O I O O
0.2 dB O O O O O O I O
0.1 dB O O O O O O O I
Sealing
Current Off X
Sink X
Source X
Channel
Bank Type D4/COT X
RT X
Loopback
Gain/Loss
Amount
0.25 dB I O O O O O O
0.5 dB O I O O O O O
1.0 dB O O I O O O O
2.0 dB O O O I O O O
4.0 dB O O O O I O O
8.0 dB O O O O O I O
16.0 dB O O O O O O I
Loopback
Gain/Loss Gain (G) X
Loss (L) X
LB Tone
Activation
w/Timer
Deactivation
4 Min.
Deactivation I O
20 Min.
Deactivation I I
No Tone LB No Tone 0 I
NOTE 1: I = IN switch position (toward the arrow or letter designation);O = OUT switch position (against the arrow or letter designation);X = Set switch toward
required label.
NOTE 2: The added attenuation in the path is the sum of the values of all switches in the IN position.

4TOLB-3L1
1306, Issue 2, May 1992
6
Attenuation
Up to 32.5 dB of attenuation in 0.1-dB steps for the TRMT path and up to 24 dB of
attenuation in 0.1-dB steps for the RCV path can be selected. TRMT attenuation is
selected at switch blocks S1 and S2; RCV attenuation is selected at switch blocks S3
and S4.
Sealing Current
Switch S5 allows selection of three sealing current modes for the channel unit:
1) In position S5-SRC, the unit provides a momentary current surge (ZAP current) and
then maintains a constant lower-level current through the T/R and T1/R1 cable pairs;
the ZAP current flows automatically when the unit is inserted into the channel bank.
The ZAP current and constant sealing current are used to assure good contact at all
cable splices by removing any high-resistance film caused by oxidation.
2) In position S5-SINK, the unit provides a circuit closure between the T/R and T1/R1
cable pairs; this selection allows current provided by equipment on the metallic side to
flow through the cable pairs.
3) In position S5-OFF, no sealing current will flow through the T/R and T1/R1 cable
pairs.
Mounting
Switch S6, which routes the TEK5,TEK6, and LOCAL LB leads to their proper card-edge
connector pins, is selected based upon the type of channel bank into which the unit will be
placed. Select the D4/COT option if using a D4 bank or a SLC 96 central office terminal.
Select RT if the bank is a SLC 96 remote terminal. Note that SLC 96 banks must be
configured to Mode 3 (special services).
Loopback Gain/Loss
This option allows loopback gain or loss selection from 0 to 31.75 dB. Gain or loss is
selected to maintain the transmission level point (TLP) levels during loopback. The
amount of gain or loss as well as the GAIN/LOSS selection is set at switch blocks S7 and
S8. Switch settings are selected as shown below.
1) Compare the TRMT input and the RCV output levels. If the TRMT level is greater
than the RCV level, select the gain (G) option; otherwise, select loss (L).
2) Subtract the TRMT level from the RCV level and take the absolute value. Round this
value to the nearest 0.25 dB. This number is the value of gain/loss to be selected.
For example, if the RCV TLP has been set to +3.5 dBm and the TRMT TLP to –10 dBm,
then the loopback gain/loss is set to the L position, and +3.5 – (–10) = 13.5 dB of loss is
selected.

7
4TOLB-3L1
1306, Issue 2, May 1992
Loopback Activation Options
The loopback circuit can be activated by one of three methods:
1) Tone Activation—Requires placement of the pc board S9-TONE switch to the IN
position and reception of the LB tone.
2) Manual Activation—Requires placement of the front-panel MAN switch to the ON
position.
3) Local Activation—Requires connection between the LOCAL LB lead (pin 45 for
D4/COT or pin 25 for RT) and the LOCAL LB GND lead (pin 19 for D4/COT or pin
23 for RT).
Loopback Time-Out
This option allows selection of the time-out interval. Set switch S9 to the 4 position for
four minutes or to 20MIN for 20 minutes. After a tone loopback activation, a second tone
should be received to deactivate the LB circuit. The timer will return the unit to the
normal, non-loopback condition if the reset tone is not received within the time-out
interval.
B. Connections
All connector pin functions are detailed in Figure 4. Connections to a prewired D4
channel bank are identified. SLC 96 connections are also shown.
The unit is a Pulsecom Type D4 plug-in module. It occupies a 1.5-inch wide mounting
space in a standard Pulsecom PD4, AT&T D4, or equivalent channel bank; see Figure 5A.
The unit can also be installed in a Pulsecom PSC-96,AT&T SLC 96, or equivalent channel
bank; see Figure 5B.
C. Adjustments
General
Alignment of the channel unit consists of selecting the desired functions by setting pc
board option switches to the appropriate positions. The procedure for selecting the
switches may be either a “prescription” or a verified “in-line” alignment.

4TOLB-3L1
1306, Issue 2, May 1992
8
Figure 4. 4TOLB-3L1 Card-Edge Connector Pin Functions
(REAR VIEW)
CARD-EDGE
CONNECTOR
PREWIRED
D4 OR SLC 96
CHANNEL BANK
CONNECTIONS
T
-12V
12G
+12V
5G
TWD
TSP(N)
TSQ(N)
RSP(N)
RNDIS
PREWIRED
D4 OR SLC 96
CHANNEL BANK
CONNECTIONS
TPAM
TPAMG
+5V
RWD
RSQ(N)
RPAM
RPAMG
FGND
50
49
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
32
31
30
29
28
54
53
52
51
CUSTOMER
INTERFACE
CONNECTIONS
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
26
27
TNEN
T1
FG
-48 F
R
R1
LOCAL LB
SG
LOCAL
LB GND
TEK 5
TEK 6
TEK 6
TEK 5
LOCAL
LB GND
LOCAL LB
-48 SP
*
*
*
*
†
†
†
†
CUSTOMER
INTERFACE
CONNECTIONS
LOOPBACK CONNECTIONS FOR D4 (OR SLC 96 COT) BANK.
LOOPBACK CONNECTIONS FOR PSC-96 OR SLC 96 RT BANK.
†
*
NOTE: MAKE INTERNAL LB CONNECTIONS TO LEADS MARKED EITHER
† OR *, BASED ON BANK CONFIGURATION, BUT NOT BOTH.

9
4TOLB-3L1
1306, Issue 2, May 1992
A. 4TOLB-3L1 Installed in a Pulsecom PD4 or AT&T D4 Channel Bank
B. 4TOLB-3L1 Installed in a Pulsecom PSC-96 or AT&T SLC 96 Channel Bank
Figure 5. Location of the 4TOLB-3L1 in Pulsecom or AT&T Channel Banks
SHELF
COMMON UNITS
(INSTALL AS SHOWN
FOR MODE 3)
B1
B2
A1
A2
PCU OIU TPU
RU LIU-3 ACU TU
RU TU
PDU
ACUBLANK
1 2 11
23
11 12
24
DIGROUP B
DIGROUP A
INSTALL THE 4TOLB-3L1
IN ANY OF THE 48
CHANNEL UNIT SLOTS
13 14
1 2
13 14
24
23
12
COMMON UNITS
(INSTALL AS SHOWN
FOR MODE 3)
PU DLU TRU
SSU CTU LIU TRU
ACU
LSU
LIU TRU
1 2 3 4
PU TRU
LIU
MXU
MXU
TWO-SHELF
GROUP
TWO-SHELF
GROUP
INSTALL THE 4TOLB-3L1
IN ANY OF THE 48
CHANNEL UNIT SLOTS
12 CHANNEL UNITS
(24 SUBSCRIBER CHANNELS)
12 CHANNEL UNITS
(24 SUBSCRIBER CHANNELS)
12 CHANNEL UNITS
(24 SUBSCRIBER CHANNELS)
12 CHANNEL UNITS
(24 SUBSCRIBER CHANNELS)
SHELF D
SHELF C
SHELF B
SHELF A

4TOLB-3L1
1306, Issue 2, May 1992
10
Prescription Alignment
This procedure consists of selecting the desired switch positions. Figure 3 shows the
location of the switches; Table 2 provides option selection instructions.
1) TRMT and RCV Attenuation—Each attenuation switch on the pc board is marked
with an attenuation value in dB, which is added to the circuit when the switch is
placed in the IN position. Set the option switches to the desired positions
corresponding to the transmit/receive attenuation and gain/loss values. TheTRMT and
RCV attenuation functions and the appropriate TLP values are shown in Figure 6. The
proper attenuation values are selected as shown below.
a) To determine the proper TRMT attenuation value, first identify the input TLP and
then apply the following formula: TRMT Attenuation = Input TLP + Insertion
Gain + 8.5 dB. For example, with an input TLP of 0 dB, the TRMT attenuation
would be 0 + 7.5 dB + 8.5 dB = 16 dB.
b) To determine the proper RCV attenuation value, first identify the output TLP and
then apply the following formula: RCV Attenuation = +4 dB + Insertion Gain –
Output TLP. For example, with an output TLP of 0 dB, the RCV attenuation
would be 4 dB + 3 dB – 0 = 7 dB.
2) Channel Bank Type, LB Mode, and Sealing Current—Select these options by placing
the switches to the proper positions. See Figure 3, Table 2, and section 3A.
Verified In-Line Alignment
This procedure uses a transmission measuring set (TMS) such as the H.P. 4937A, the
front-panel TEST jack of the unit, and MAC jack to bantam jack adapter, such as the
Pulsecom B105097 or equivalent.An extender card can be used to provide easy access to
Figure 6. 4TOLB-3L1 Level Settings
17
- 8.5 dB
TLP
+4 dB
TLP
TRANSMIT PATH
TRMT ATTN =
INPUT TLP + 16 dB
RCV ATTN =
7dB - OUTPUT TLP
RECEIVE PATH
+7 dB to
-17 dB TLP
P/O J1
P/O J1
TRMT
+7.5 dB
+3 dB
0 to
32.5 dB
S1 & S2
3 9
0 to
24 dB
S3 & S4
TO
CHANNEL
BANK
+16.5 dB to
-16 dB TLP
RCV
T
R
0 to
±31.75 dB LOOPBACK
PATH
LB
LB

11
4TOLB-3L1
1306, Issue 2, May 1992
the card-edge connector pins and pc board switches. The alignment procedures and test
equipment setups are shown in Figure 7. A brief description of the TEST jack and adapter
is given below.
1) TEST Jack—The MAC jack (J1) on the front panel of the unit permits the insertion of
a test card for alignment and measurement of circuit parameters. Additional
information on the MAC jack is given in section 6, Maintenance.
2) Adapter—The MAC jack to bantam jack adapter provides bantam jack access to
the test points available through the MAC jack on the front panel of the channel unit.
The adapter can be the Pulsecom B105097 MAC jack to bantam jack adapter or
equivalent.A detailed description of the B105097 is provided in Pulsecom Practice
Section 1303.
4. CIRCUIT DESCRIPTION
A. VF Transmit Operation
The following paragraphs describe the operation of the channel unit as shown in Figure 8,
Functional Diagram. VF signals enter the channel unit through the transmit input port
(T and R leads), where a transformer provides DC isolation and maintains the required
600-ohm impedance.
The signals then are coupled through the transmit amplifier to the attenuator circuit, which
provides from 0 to 32.5 dB of attenuation in 0.1-dB steps. The attenuation switches are
selected to obtain the required transmission level (–8.5 TLP) at the transmit path TEST
jack (J1-1/7). TheVF signals are filtered and routed to the transmit sampling gate.
The common equipment, which handles 8000 frames of information per second, causes
the transmit sampling gate to close during the proper channel in each frame.At the proper
channel time, when the TWD, TSP(N), and TSQ(N) leads are all at logic one, the control
lead to the transmit sampling gate switches to logic zero to allow the common equipment,
through the transmit output port (leads TPAM and TPAMG), to sample and encode the
voice signal at that instant.
The TNEN output is at logic zero when the transmit input control leads, TSP(N) and
TSQ(N), are both at logic one. This output indicates to the D4 common equipment
transmit unit that the selected voice-type channel unit is installed in the channel bank.
The TEST jack (J1), accessible from the front panel, allows access to the transmit voice
path for test purposes. A test card inserted into the J1 jack provides access to the output of
the attenuator (terminal J1-1) and the input of the transmit filter (terminal J1-7).

4TOLB-3L1
1306, Issue 2, May 1992
12
STEP ACTION
1Plug the B105097 MAC Jack to Bantam Jack Adapter into the TEST jack on
the front panel of the near-end 4TOLB-3L1; arrange to have another adapter
installed into the TEST jack of the far-end unit.
2 Set the TMS1 in the bridged mode and adjust the TMS1 oscillator output for
a 1004-Hz tone at the desired TRMT input level (between +16 dB and
–16 dB TLP). Connect the oscillator to the TRMT IN port (connector pins 24
and 51) and the level meter to the TX TLP port (jack J2–TX TLP of the MAC
Jack to Bantam Jack Adapter).
3 Vary the near-end TRMT attenuation to achieve a level meter reading of
–8.5 ± 0.25 dBm.
4 Arrange with the far end to set the TMS2 in the bridged mode, to
connect the TMS2 level meter to the RX TLP port (jack J2–RX TLP of the
MAC Jack to Bantam Jack Adapter), and to verify a level meter reading of
+4.0 ± 0.25 dBm.
5Arrange with the far end to move the TMS2 level meter to the RCV OUT port
(connector pins 20 and 47), to set the TMS2 in the terminated mode, and to
vary the RCV attenuation switches to attain the desired RCV output.
A. Near-End TRMT and Far-End RCV Alignment
Figure 7. TRMT, RCV, and LB Alignment Procedures andTest Equipment Setups
-8.5
±0.25
dBM
OSCILLATOR
1004 Hz
(+16 dB to -16 dB TLP)
TMS 1
(BRIDGED MODE)
SET TO
DESIRED
LEVEL
X
F
M
R
LEVEL METER
MAC TO BANTAM
ADAPTER
NEAR
END
9
1
7
3
0 to 32.5 dB
0 to 24 dB
T1
R1
TRANSMIT PATH
RECEIVE PATH
A
P/O
J2 TX
TLP
MODEL 4TOLB-3L1 UNDER TEST
P/O J1
P/O P1
+4.0
±0.25
dBM DESIRED
RCV TLP
OUT
P/O TMS 2
(BRIDGED MODE)
MAC TO BANTAM
ADAPTER
FAR
END
7
3
9
1
P/O J1 P/O P1
T1
R1
TRANSMIT PATH
RECEIVE PATH
RX
TLP
LEVEL METER LEVEL METER
P/O TMS 2
(TERMINATED MODE)
+7.5
dB
+3
dB
TRMT
IN T
R
24
51
B
P/O
J2
P/O J1
P/O P1
TO/FROM
CHAN. BANK
RCV
OUT
47
20
T
R
A
P/O
J2
P/O J1 P/O P1
B
P/O
J2
TO/FROM
CHAN. BANK
X
F
M
R
X
F
M
R
X
F
M
R
0 to ±31.75 dB
LB
LB

13
4TOLB-3L1
1306, Issue 2, May 1992
STEP ACTION
1Arrange with the far end to set the TMS2 in the bridged mode and to adjust
the TMS2 oscillator output for a 1004-Hz tone at the desired TRMT input
level (between +16 dB and –16 dB TLP). Also arrange to connect the
oscillator to the TRMT IN port (connector pins 24 and 51) and the level meter
to the TX TLP port (jack J2–TX TLP of the MAC Jack to Bantam Jack
Adapter).
2 A level meter reading of –8.5 ± 0.25 dBm can be achieved by varying the
far-end TRMT attenuation.
3 In the near end set the TMS1 in the bridged mode and connect the TMS1
level meter to the RX TLP port (jack J2–RXTLP of the MAC Jack to Bantam
Jack Adapter). Verify a meter reading of +4.0 ± 0.25 dBm.
4 Move the TMS1 level meter to the RCV OUT port (connector pins 20 and 47)
and set the TMS1 in the terminated mode.Vary the RCV attenuation switches
to attain the desired near-end RCV output.
B. Near-End RCV and Far-End TRMT Alignment
Figure 7. TRMT, RCV, and LB Alignment Procedures andTest Equipment Setups (Continued)
MAC TO BANTAM
ADAPTER
NEAR
END
X
F
M
R
9
1
7
3
0 to 32.5 dB
0 to 24 dB
T1
R1
TRANSMIT PATH
RECEIVE PATH
B
P/O
J2
MODEL 4TOLB-3L1 UNDER TEST
P/O J1 P/O P1
MAC TO BANTAM
ADAPTER
FAR
END
7
3
9
1
P/O J1 P/O P1
TRANSMIT PATH
RECEIVE PATH
+7.5
dB
A
P/O
J2
P/O J1 P/O P1
TO/FROM
CHAN. BANK
P/O
J2
P/O J1 P/O P1
B
P/O
J2
TO/FROM
CHAN. BANK
T
R
-8.5
±0.25
dBM
OSCILLATOR
1004 Hz
(+16 dB to -16 dB TLP)
TMS 2
(BRIDGED MODE)
LEVEL METER
TX
TLP
TRMT
IN
24
51
+3
dB
+4.0
±0.25
dBM
DESIRED
RCV TLP
OUT
P/O TMS 1
(BRIDGED MODE)
T1
R1
RX
TLP
LEVEL METERLEVEL METER
P/O TMS 1
(TERMINATED MODE)
RCV
OUT
47
20 T
R
AX
F
M
R
X
F
M
R
X
F
M
R
0 to ±31.75 dB
LB
LB

4TOLB-3L1
1306, Issue 2, May 1992
14
STEP ACTION
1Arrange with the far end to set the TMS2 in the bridged mode.Also arrange to
adjust the TMS2 oscillator output to the same frequency and level used in
Step B-1, to connect the TMS2 oscillator to the TRMT IN port (connector
pins 24 and 51), and to connect the TMS2 level meter to the RCV OUT port
(connector pins 20 and 47).
2 In the near end set the loopback attenuation switches OUT and the gain/loss
setting to LOSS.
3 Activate the near-end LB circuit either by setting the front-panel LB switch
ON or by arranging with the far end to inject a 2713-Hz tone of proper level
(0 to –30 dBm0) and duration (> 2.5 seconds).
4 Request the far end to observe whether the TMS2 level meter reading is
higher or lower than it was in Step A-5.
A) If the level is higher, leave the gain/loss setting on LOSS.
B) If the level is lower, set the gain/loss selection to GAIN.
5 Vary the loopback attenuation settings on the near end to achieve the same
RCV OUT level that was attained in Step B-4.
6 Unloop the near-end unit.
C. Loopback Alignment
Figure 7. TRMT, RCV, and LB Alignment Procedures andTest Equipment Setups (Continued)
NEAR
END FAR END
0 to 32.5 dB
0 to 24 dB
T1
R1
MODEL 4TOLB-3L1 UNDER TEST
(LOOPBACK MODE ENABLED)
7
3
9
1
P/O J1
TRANSMIT PATH
RECEIVE PATH
+7.5
dB
P/O J1
TO/FROM
CHAN. BANK
T
R
+3
dB
X
F
M
R
X
F
M
R
0 to ±31.75 dB
LB
LB
X
F
M
R
9
1
7
3
TRANSMIT PATH
RECEIVE PATH
P/O J1P/O J1
TO/FROM
CHAN. BANK
T1
R1
T
R
X
F
M
R
TMS-2
47
20
24
51 TRMT
IN
BRIDGED
MODE
1004 Hz
(+16 dB to
-16 dB TLP)
NOTE: RCV TLP OUT MUST
BE SAME AS NEAR END RCV
OUT LEVEL IN TEST PART B.
DESIRED
RCV TLP
OUT

15
4TOLB-3L1
1306, Issue 2, May 1992
Figure 8. 4TOLB-3L1 Functional Diagram
20 T1
47 R1
4
MIN
TRANS-
FORMER
TRMT
ATTN
0 to 32.5 dB
S1 & S2
45 LOCAL
LB
25 LOCAL
19 LOCAL
LB GND
LB GND
LB*
*
CUSTOMER
INTERFACE
CONNECTIONS
P/O S6
D4/COT
D4/COT
RT
RT
SOURCE
TRANS-
FORMER
LB
17
TRMT
-8.5 dB
TLP
TRMT
FILTER
28
GND
NC
+12 dB
BOOST
LB
LOGIC
LB
RELAY
TONE
20
MIN
S9
LB MODE
LB
INDICATOR
-48 SP
2713 Hz
DETECT
39
RCV
+4 dB
TLP RCV
FILTER
RCV
GATE
RPAM
RPAMG
410
RNDIS
14
TRMT
GATE
TPAM
TPAMG 28
29
TWD 6
TSP(N) 7
TSQ(N) 8
TNEN 32
RWD 39
RSP(N) 13
RSQ(N) 40
PREWIRED
CHANNEL
BANK
CONNECTIONS:
PD4, PD4-24,
PD4-48, or
PSC-96
CONTROL
LOGIC
41
42
NOTE: POWER SUPPLY LEADS
ARE NOT SHOWN
LB RCV
ATTN
0 to 24 dB
S3 & S4
23 LOCAL
46 TEK 5
52 TEK 5
48 TEK 6
CUSTOMER
INTERFACE
CONNECTIONS
G/L NETWORK
0 to 31.75 dB
S7 & S8
12dB
ATTN MAN
LB
NO SC
NO SC
SINK
SINK
LB
SOURCE
S5
SEALING
CURRENT
REGULATOR
LB
-48 F
P/O S6
D4/COT
D4/COT
RT
RT
TEK 5
TEK 6
LB
*
*
TEK 6
49
*SHOWS LOOPBACK CONNECTIONS FOR PSC-96 OR SLC 96 RT BANK ONLY.
+5 V
P/O CARD-EDGE
CONNECTOR
P/O CARD-EDGE
CONNECTOR
24
51
T
R
LB

4TOLB-3L1
1306, Issue 2, May 1992
16
B. VF Receive Operation
At the proper channel time, when the RSP(N), RSQ(N), and RWD leads are all at logic
one, the receive sampling gate closes to receive a sample at the receive input port (leads
RPAM and RPAMG). This action is repeated at every frame (8000 times per second), thus
restoring the waveform from the received digital samples. The signals from the receive
input bits are presented to the receive filter. The filter, which has a low-pass characteristic,
provides an output impedance of 600 ohms and brings the signal to the required +4 TLP.
This level is accessible at the receive TLP TEST jack (J1-3/9).
The front-panel TEST jack allows access to the receive voice path for test purposes. A test
card inserted into the J1 jack provides access to the output of the receive filter (terminal
J1-9) and the input of the receive attenuator (terminal J1-3).
Filtered VF signals are presented to the attenuator circuit, which provides from 0 to 24 dB
of attenuation in 0.1-dB steps. The attenuation switches are selected to obtain the
desired output level. Signals from the attenuator are routed through the receive
amplifier circuit and the transformer circuit to become available at the receive output port
(T1 and R1 leads).
C. Loopback Circuit
Activation
The LB circuit can be activated by one of three independent methods:
1) Tone Activation—The LB tone (2713 Hz) must be received at the receive input
RPAM for 2.5 seconds or longer and then removed to activate the loopback mode. LB
activation upon removal of the initial tone burst (rather than during) prevents
accidental looping at other LB points on a multi-point circuit. LB deactivation occurs
upon reception of a second LB tone of at least 0.6-second duration. Unlike LB tone
activation, the LB release sequence occurs during application of the tone. The first LB
tone will activate the LB circuit and start a timer. The electronic timer will time out
and the unit will return to the normal, non-looopback condition if the LB deactivation
tone is not received within either 4 or 20 minutes (depending upon the setting of
switch S9).
2) ManualActivation—Place the LB MAN switch accessible from the front panel in the
ON (up) position to force the module into the LB mode. Return the switch to the OFF
(down) position to release the module from this mode.
3) Local Activation—External connection of LOCAL LB lead, pin 45 (D4/COT mode)
or pin 25 (RT mode), to pin 19 (LOCAL LB GND lead) or pin 23 (PSC-96 RT)
activates the LB circuit. In the D4 mode only, this connection may be controlled by
either a switch or a relay contact.

17
4TOLB-3L1
1306, Issue 2, May 1992
External LB (K3) Relay Contact
The normally closed LB relay contact, which internally connects TEK5, pin 46 (D4/COT
mode) or pin 52 (RT mode), and TEK6, pin 48 (D4/COT mode) or pin 49 (RT mode),
opens during loopback operation. The TEK5 and TEK6 leads can be used to disable an
externally connected modem.
Remote Testing
When the unit is in loopback mode, the transmit and receive ports (T, R, T1, and R1 leads)
are disconnected. The sealing current is also disabled. The transmit and receive paths are
internally connected through the gain/loss network so that the unit can be tested from the
far end. The gain/loss network is configured to maintain the transmission level point at the
transmit TLP and beyond during loopback. The front-panel LB indicator glows whenever
the unit is in the loopback mode.
5. SPECIFICATIONS
Table 3 lists the electrical and physical characteristics of the unit.
6. MAINTENANCE
The channel unit is composed of solid-state circuits. No routine maintenance is required to
keep the unit operating properly. In case of equipment malfunction, use the test card
(standard AT&T P6AD cord or Pulsecom B105097 adapter) and measurements of input
and output signals to determine the trouble source. The TEST jack provides access to the
TRMT TLP, the RCV TLP, and the T and R leads; it also provides a means of removing
the RNDIS RCV disable signal. See Figure 9.
Figure 9. 4TOLB-3L1 Test Points
7
8
9
10
11
12
1
2
3
4
5
6
TRMT
FILTER TRMT ATTN
NC
TPU CKT
NC
RCV
FILTER
GND
RCV ATTN
CHAN.
LOGIC
NC
NC
TRMT
GND
RNDIS
RCV
T
E
S
T
NC

4TOLB-3L1
1306, Issue 2, May 1992
18
Table 3. 4TOLB-3L1 Specifications
Parameter Condition Value
A. Transmission
Nominal Impedance T, R and T1, R1 600 Ω
TRMT Input Level a) Nominal
b) Range –16 dBm –16 to +16.5 dBm
RCV Output Level a) Nominal
b) Range +7 dBm –17 to +7 dBm
TRMT TLP –8.5 dBm
RCV TLP +4.0 dBm
TRMT Attenuation a) Range
b) Resolution
c) Steps
0 to 32.5 dB
.1 dB
.1, .2, .4, .8, 1.6, 3.2, 6.4, 12.8 dB
RCV Attenuation a) Range
b) Resolution
c) Steps
0 to 24 dB
.1 dB
.1, .2, .4, .8, 1.5, 3, 6, 12 dB
Frequency Response 300 to 3000 Hz ± 0.15 dB
Return Loss 600 Ω
a) 1000 Hz
b) 300 to 3000 Hz
≥ 28 dB
≥ 23 dB
Longitudinal Balance
(Ref. –16 TLP) a) 200 to 1000 Hz
b) 3000 Hz > 74 dB > 69 dB
Crosstalk 700 to 3000 Hz ≤ –71 dB
Idle Channel Noise a) Overall
b) TRMT
c) RCV
≤ 20 dBrnC0
≤ 17 dBrnC0
≤ 17 dBrnC0
Nominal Sealing Current Typical
a) 0 k Ω loop
b) 2 k Ω loop 30 mA 22 mA
ZAP Sealing Current Typical, 0 k Ω loop 60 mA

19
4TOLB-3L1
1306, Issue 2, May 1992
B. Loopback Parameters
Manual LB Activation
Via PC Board MAN Switch a) Switch on
b) Switch off LB ON LB OFF
Tone LB Activation (in RCV Input Port)
Tone Frequency 2713 ±7 Hz
Tone Level Ref. at RX Facility port –30 to 0 dBm
Tone Duration for LB ON LB ON after tone removal 2.5 seconds
Tone Duration for LB OFF LB release during tone 0.6 second
Timer LB Deactivation Selectable 4 or 20 minutes
LB Level
LB Gain a) Range
b) Resolution
c) Steps
0 to ±31.75 dB
.25 dB
.25, .5, 1, 2, 4, 8, 16
C. Power Requirements
–48 VDC Supply a) Range
b) Ripple, 120 Hz
c) Sealing current off, no loopback
d) Maximum
e) Power drain, max.(with nominal sealing current)
f) Heat dissipation, max. (with nominal sealing current)
–42.25 to –52.5 VDC
250 mV
3.5 mA
40 mA
1.92 W
1.92 W
–12 VDC Supply a) Tolerance
b) Max. current
c) Max. power drain
d) Max. heat dissipation
–12 VDC ±5%
15 mA
180 mW
180 mW
+12 VDC Supply a) Tolerance
b) Max. current
c) Max. power drain
d) Max. heat dissipation
+12 VDC ±5%
17 mA
204 mW
204 mW
+5 VDC Supply a) Tolerance
b) Max. current
c) Max. power drain
d) Max. heat dissipation
+5 VDC ±10%
10 mA
50 mW
50 mW
Power (with Sealing
Current Source) a) Max. power drain
b) Max. heat dissipation 2.33 W 2.33 W
Table 3. 4TOLB-3L1 Specifications (Continued)
Parameter Condition Value

4TOLB-3L1
1306, Issue 2, May 1992
20
Pulse Communications Inc.
A Subsidiary of HUBBELL INCORPORATED
2900 Towerview Road
Herndon, Virginia 20171–3286
PRINTED IN USA
Customer Service
For technical support:
International — 703-478-7077
Domestic — 1-800-841-1005
E-mail — [email protected]
For order information: 1-800-381-1997
For product literature: 1-800-699-6006
7. CUSTOMER SERVICE
Questions concerning the operation of the unit can be directed to Pulsecom Customer
Service. Pulsecom does not recommend that repairs be performed in the field. Repair
services are available and can be obtained by returning the defective unit to the Pulsecom
Repair Department.
CAUTION
Check that the switches on the replacement unit are in the same position
as those on the unit that was removed to ensure proper operation.
D. Environmental
Operating Temperature a) D4/SLC 96, COT
b) SLC 96, RT 0°to +55°C –40°to +85°C
Relative Humidity No condensation Up to 95%
Size (height x width x
depth) a) Inches
b) Centimeters 4.4 x 1.4 x 10 11.1 x 3.5 x 25.4
Weight a) Ounces
b) Grams 10 280
Table 3. 4TOLB-3L1 Specifications (Continued)
Parameter Condition Value