Charles Industries 31929E - Manual (Page 7)

Section 319-29E-202
7
3.1 Signal Transmission Paths
In the idle (Looped down) mode, the signal from the network is coupled to the unit and routed through the trans-
mit pad circuit. Switch S4 mounted on the circuit pack is used to adjust the transmit pad which consists of two
cascaded 7.5dB sections, allowing transmit path losses of 0, 7.5 and 15dB.
The signal from the customer is routed through the receive side of the 3192–9E. This side contains a signal re-
generator with a wide range ALBO, accommodating signal levels from 0 to –35dB. After regeneration, the signal
is passed through a fixed DSX–1 pre-equalizer which will accommodate up to 110 feet of 22ga or 90 feet of 24ga
cable to the DSX–1 point.
3.2 Signal Loopback Operation
The signal from the network is continually monitored by the Loopback Code Detector for Loopback control se-
quences from the network. The detector will automatically configure itself to recognize either inband (SF) or data
link (ESF) control sequences. When the detector detects ESF framed traffic, it will only recognize Loopback con-
trol sequences in the ESF data link. In addition, when ESF traffic is present, the unit’s front panel ESF indicator
(green) will light.
3.3 Loopback Activation (State 1 ' State 2)
To activate loopback utilizing the SF protocol, a repetitive pulse pattern of two ones followed by three zeros
(11000) or one one followed by five zeros (100000) is applied to the line. The Code Detector will reject the pulse
pattern if it is less than 5 seconds in duration or if its error rate is greater than 10-
#
. The circuitry will accept a
pulse pattern if it is greater than 5 seconds in duration.
To activate loopback utilizing the ESF protocol, the Code Detector monitors the 4kHz Data Link Channel of the T1
bit stream for the following repetitive pulse pattern; 0 001001 0 11111111 where the rightmost bit is transmitted
first. The pattern is acknowledged as valid when it has been received by the Code Detector four consecutive
times. This corresponds to 16ms.
The unit can manually be placed in the loopback state by momentarily operating the recessed front panel MLB
pushbutton switch.
After the code pattern is detected for the proper duration or a MLB pushbutton operation is detected, the Loop-
back Controller will operate the LB Relay.
3.3.1. Loopback Mode (State 2)
When the unit is in the loopback state, the CPE equipment is disconnected from the network and terminated in
100 ohms. The signal from the network is looped back toward the network. The front panel LB LED (amber) is on
and an AIS (all ones) signal is sent toward the Customer Interface.
3.3.2. Loopback Timeout/Retrigger
The 3192–9E provides a fixed 20 minute loopback timeout. Normally after 20 minutes the loopback state will
timeout and release. When the 3192–9E is in loopback, a reapplication of any of the loopback activation se-
quences will reset the timer for a new 20 minute period.
3.4 Loopback Deactivation (State 2 ' State1)
To deactivate loopback utilizing the SF protocol, a repetitive pulse pattern of 3 ones followed by 2 zeroes (11100)
or 1 one followed by 2 zeroes (100) is applied to the line. The Loopback Code Detector will reject the pulse pat-
tern if it is less than 5 seconds in duration or if its error rate is greater than 10-
#
. The Loopback Code Detector will
accept a pulse pattern if it is greater than 5 seconds in duration.
To deactivate loopback utilizing the ESF protocol, the Code Detector monitors the 4kHz Data Link Channel of the
T1 bit stream for the following repetitive pulse pattern; 0 010010 0 11111111 where the rightmost bit is trans-
mitted first. The pattern is acknowledged as valid when it has been received by the Code Detector four consecu-
tive times. This corresponds to 16ms.
To deactivate loopback manually, the front panel MLB push button switch is momentarily operated.
When loopback is deactivated, the Loopback Controller releases the LB relay, restoring the thru transmission path
from network to CPE, extinguishing the LB LED, and removing the AIS signal that was being sent toward the
Customer Interface.