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Methods of Call Recording
There
are several ways to record calls, each of which has its
own advantages and drawbacks. It is important to
understand what options are available to you and
determine which of the various configurations would best
fit your needs.
Extension Recording
Sometimes known as ‘station recording’ or ‘handset
recording’, this kind of system records calls direct
from the PBX handsets. In an extension recording
configuration calls are recorded from behind the PBX.
Typically this enables the recorder to pick up a larger
set of data about the call via the D- channel and also
allows the recorder to record internal calls, track the
call through the system and cope better with
free-seating or hot-desking arrangements. If you opt for
an extension recording system you are not likely to
require any other kind of integration to the PBX such as
SMDR or CTI.
Extension devices are wide and varied with a multitude
of vendors and devices that may be handsets, headsets,
analogue phones, turrets, dealer boards, microphones and
speakers.
The
diagram below illustrates the basic configuration of an
extension recording system. Note how the recording
device interfaces directly with the PBX handsets (or
headsets, turrets etc), rather than the PSTN trunk.
Please
note that no wiring goes directly to the handset, all
connectivity is done on your PBX ‘patch panel’.

Trunk Side Recording
Sometimes known as ‘line side recording’, a trunk
recording solution interfaces directly with the analogue
or ISDN PSTN trunks before they reach the PBX system.
Trunk side recording uses high impedance ‘passive tap’
technology to interface to the incoming trunks without
terminating the line or impacting on the strength of the
signal. In these kinds of configurations the incoming
trunks are fitted with ‘T – splitters’ or ‘RJ45
doublers’, small pieces of kit fitted to the lines which
divert the E1 signal directly into the recorder.
Unlike
an extension recording system, trunk recorders do not
always interface with the PABX. This means that a basic
trunk solution will not provide the recorder with
details such as extension/agent data and will only
present the recorder with basic information from the
D-channel such as time/ date and CLI for archival. It is
usual therefore when implementing a trunk solution, to
perform some kind of bespoke integration with the PABX
in order to gather this missing agent/extension
information. This is usually achieved by integrating
with the SMDR or CTI ports on the PBX and such
integration allows specified extensions to be excluded
from recording. It is important to understand how you
wish to search for your recorded calls and establish
whether SMDR or CTI integration is required to achieve
this, you may require an additional license on your PBX
to enable this functionality.
The
diagram below illustrates the basic configuration of a
trunk recording solution. Note how the recorder
interfaces directly with the incoming lines rather than
the extensions and how an optional SMDR or CTI
integration can be added.

Trunk or
Extension Side Recording: which is most suitable for
you?
This is
usually the key driver behind which solution you look to
purchase, the following advantages and disadvantages
that need to be carefully considered when deciding your
requirements: -
In terms
of functionality, recording at the extension offers a
more comprehensive solution than trunk recording.
Extension recording will allow you to record internal
calls, track holds and transfers and will also provide a
more complete set of data on which extension took the
call without the need for further integration with the
PBX. The disadvantage of extension recording when
compared to trunk is cost – digital extension recording
tends to be slightly more costly than trunk recording
when compared on a channel for channel basis.
Trunk
recording allows you to capture all calls that use the
recorded trunks so tends to be better suited to
environments where organisations need a blanket
recording solution. The downside of this is that without
some form of PBX integration (SMDR or CTI) at further
additional cost, there will be no information on the
handsets presented to the recording system, and all
handsets, including those of management and HR will be
recorded. SMDR and CTI provide a commonly used
workaround for this but there are cost implications
here, particularly with CTI integration. |