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Voice Modules (VCMs & DPVs)
DPV Overview
The OCM Dual Private Voice (DPV) module is a two-channel analog voice compression module
that operates at speeds of 4.8, 6.4, 8 or 9.6 kbps. There are six DPV cards, one for each signaling
interface: FXS, FXO and E&M with or without FAX bypass. Additionally, there is a seventh DPV
version which provides ground start signaling on an FXO interface. The FXS interface handles both
loop start and ground start signaling. Each provides two independent channels per module
occupying one slot in an OCM enclosure or shelf. Echo cancellation is standard on all versions, and
the DPVs require no additional bandwidth for signaling.
The DPV modules provide:
•
FXS and FXO Loop Start and Ground Start, and E&M telephony interfaces
•
CS-ACELP voice compression at 9600, 8000 bps
•
IMBE voice compression at 9600, 8000, 6400, 4800, and 2400 bps (OCM-1000 or OCM-
2000 with GTS 2.2 only)
•
FAX bypass (ITU-T Group 3)
•
Integral echo cancellers
•
Software programmable transmit and receive levels
•
Internally generated ringing and battery for short loops
•
Optionally, external battery and ringing for long loops
•
Downloadable software
Note
The DPV cards are not end-to-end compatible with previous OCM and TMS voice channel cards.
DPV modules convert incoming voice signals into compressed speech using CS-ACELP
(Conjugate Structure Algebraic Code Excited Linear Prediction) or IMBE (Improved Multiband
Excitation) speech encoding. The compressed voice is transported within the OCM network and
terminates on another DPV or VTP module at a remote location.
The DPV modules provide FAX modem compatibility and FAX bypass (ITU-T Group 3) which
allows interconnection of FAX machines. FAX documents may be transmitted across the network
at a rate up to the voice compression rate specified. The FAX machines may be directly connected
to an FXS port or indirectly through a PBX or the public network. FAX mode of operation is
automatically entered upon detection of the 2100 Hz tone generated by the answering FAX
machine. Machines which exclusively use the DIS method of handshake are not supported. The
FAX machines may be either set to auto answer or manually initiated during a voice call. For
purposes of the automatic routing of FAX calls, the 1100 Hz calling tone will pass through the voice
algorithm.
Figure 6-3
and
6-12
Figure 6-4
illustrate several typical DPV applications.
Office Connunications Manager OCM-1000/OCM-2000
Installation & Operation
DPV Overview
036R340-000
Issue 16
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