4
X
E1/G.703 P
LESIOCHRONOUS
M
ULTIPLEXER
O
PERATING
M
ANUAL
IOA77-1F
8
May 2007
3 F
UNCTIONAL DESCRIPTION
TM-77 and MD-77 devices perform the following functions:
1. processing of electrical signals at the bit rate of 2.048 Mbit/s in HDB-3 three-level code into
a digital signal in the natural code;
2. multiplexing of four data streams at the bit rate of 2.048 Mbit/s according to the G.742
recommendation;
3. encoding in 5B/6B code;
4. processing an electrical signal into an optical one;
5. receiving of an optical signal and processing it into an electrical signal;
6. decoding of a data stream encoded in 5B/6B code;
7. demultiplexing of four data streams at the bit rate of 2.048 Mbit/s;
8. encoding of a data stream at the bit rate of 2.048 Mbit/s in HDB-3 code;
9. control and signaling of the basic parameters of the multiplexer operation and generation
of alarms in the event of failures.
3.1 Diagnostic and signaling systems
TM-77 and MD-77 type devices automatically control the parameters of E1/G.703 local
interface and linear optical signal, and detect and signalize the following conditions and values:
G.703 E1 local interface
•
loss of interface input signal
•
receiving of AIS signal coming from E1 interface
•
receiving of AIS signal coming from demultiplexer
•
HDB3 code violation
Linear optical interface:
•
loss of linear input signal
•
loss of frame synchronization of the received signal
•
block error rates 1x10
-3
and 1x10
-6
exceeded
•
receiving of the AIS bit in G.742 frame signaling a remote alarm
An alarm condition is indicated as follows:
•
appropriate local interface LED is switched on: LOES
•
appropriate optical interface LED is switched on: LOOS, LOF, 10
-3
, 10
-6
, RAL, LDF
•
shorting of UALA, NUALA alarm relay terminals in TM-72 telecommunication rack.
When a failure is detected, a "non-urgent" alarm – NUA (indicating a failure condition,
which does not interrupt transmission) or an "urgent" alarm – UA (meaning a transmission
interruption - an immediate operator's response is necessary) is generated.
MD-77 device card signalizes generation of an urgent or non-urgent alarm by sending
a signal to activate the alarm relays in TM-72 rack. The urgent and non-urgent alarm signaling
relay contacts in the telecommunication rack are connected to DSUB- 9 female socket.
The detected failure conditions and actions taken are shown in Table 1.
