Datacom DM991C, Product Manual

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Product Manual - DM991 Series V Family - 204.4092.08 73
1 2 3 4 5 6 7 8
0 0 0 0 0 X0 Y X1 X2
1 A1 B1 C1 D1 A16 B16 C16 D16
2 A2 B2 C2 D2 A17 B17 C17 D17
3 A3 B3 C3 D3 A18 B18 C18 D18
4 A4 B4 C4 D4 A19 B19 C19 D19
5 A5 B5 C5 D5 A20 B20 C20 D20
6 A6 B6 C6 D6 A21 B21 C21 D21
7 A7 B7 C7 D7 A22 B22 C22 D22
8 A8 B8 C8 D8 A23 B23 C23 D23
9 A9 B9 C9 D9 A24 B24 C24 D24
10 A10 B10 C10 D10 A25 B25 C25 D25
11 A11 B11 C11 D11 A26 B26 C26 D26
12 A12 B12 C12 D12 A27 B27 C27 D27
13 A13 B13 C13 D13 A28 B28 C28 D28
14 A14 B14 C14 D14 A29 B29 C29 D29
15 A15 B15 C15 D15 A30 B30 C30 D30
Y is the Yellow Alarm remote multiframe. When in 1 indicates that the alarm is
activated.
The MAS is defined as the timeslot 16 that has the 0000xyxx sequence and can be in
the frames that have FAS as well as in the ones that do not.
Frame #
bits 1 to 8 of timeslot 16 of each frame
Ai-Di are the channel signaling bits. Channel numbers refer to phone channels.
Timeslots 1 to 15 and 17 to 31 correspond to the phone channels 1 to 30.
X0-X2 are the x bits of the G.704 regulation, usually set to 1.
Table 21. CAS Multiframe Structure
16.2. Electrical Characteristics
The E1 line signal follows the HDB3 (High Density Bipolar 3) coding from ITU G.703 recommendation,
which is an improvement in the AMI (Alternate Mark Inversion) coding.
In the AMI code, mark is transmitted as alternate positive and negative pulses, while spaces are
transmitted as zero level voltage. AMI cannot transmit a long zero sequence because as there are no
signal variations on the line, the receiver will lose signal timing.
For the HDB3 format, mark is coded as for the AMI code, but four consecutive zeros (spaces) are
replaced by a 000V or B00V sequence. The choice of one or other is done in such way that the number of
B pulses between V consecutive pulses is odd, meaning successive V pulses have alternate polarity in
order that no DC component is introduced in the signal. The Figure 34 shows an application example of
HDB3 coding in a bit sequence.