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Main Module Of The 3U G.711/G.722 ISDN Codec System

Features Description Downloads Ask a Question
  • Contains Two Codecs & Terminal Adapter
  • Connects directly to an ISDN2 S bus
  • Make ordinary telephone calls (G711)
  • Use as near perfect telephone balance unit Use for broadcast sound (G722)
  • No extra circuits required for installation
  • Use existing audio circuits for control
  • Dial & Configure using DTMF
  • Recorded messages provide information to the user
  • 3U Module only 7E wide x 160mm deep
  • Up to 10 modules can be fitted in a 3U subrack
  • Also available in standalone 'brick' style

Designed for broadcast use, this module is very compact and permits a large number of codecs to be installed in a small space. Each codec can be configured to use the G711, the G722 or either algorithm. Because the G711 algorithm is the standard used for ordinary telephones it is possible to make ordinary telephone calls. More remarkably, the GSGC9 can also be used as two telephone balance units with perfect separation between the go and return circuits.

The G722 mode provides 7.5kHz circuits and is commonly used by the broadcasters for news, sport and current affairs. Frame alignment of the G722 signal is achieved by statistical analyses of the incoming data, but the outgoing data is network aligned.

Because DTMF signals are used to control the GSGC9 and recorded messages are used to let the user know the call progress, it is entirely practical to install these modules in an apparatus room and control them from a studio with no control circuits required. All information goes to and from the studio on the ordinary programme and audio pairs.

Audio inputs and outputs can be plugged into bantam jacks on the front panel or wired into the multiway DIN plug on the module rear. All inputs and outputs are zero level balanced.

Designed originally to work with our international co-axial commentators units, this new range of ISDN equipment provides a large number of broadcast ISDN facilities in a small space. It is based on a 3U modular system, the main item of which is a 3U module coded GSGC9 which contains a terminal adapter and 2 codecs. Being only 7E (1.4 inches) wide, it is possible to fit up to ten GSGC9 modules (i.e. 20 codecs) into a 19 inch subrack and still leave room for the mains power unit. We can supply a number of suitable subracks varying only on the connectors fitted to the rear panel.

An RJ45 lead connects the GSGC9 to a standard ISDN2 bus. Both B channels of the ISDN2 network can be used simultaneously by the terminal adapter fitted in the GSGC9. Each B channel is connected to one codec. The module is capable of being used on a variety of different national network types.

Each GSGC9 module contains two independent codecs. Each codec can operate with the G722 or G711 algorithms. The user can independently configure each of the two codecs to operate on the G722, the G711 or either algorithm.

The G711 algorithm is the standard used for ordinary telephones and so it is possible to make normal telephone calls or use the module as two telephone balance units that will give perfect separation between the go and return circuits.

The G722 algorithm is commonly used by the broadcasters for news, sport and current affairs. It provides a 7.5kHz mono circuit.

Two audio inputs and two audio outputs (one for each codec) are provided on the GSGC9 terminated on front panel bantam jacks. They can also be wired out to the rear panel of the 3U subrack. Our standard subrack does not have these circuits wired out but we do make two other versions of the subrack, one with four rear panel 38 way Varicons and the other with forty rear panel XLRs.

No operational controls are fitted on the GSGC9 modules. All communication with the module is with DTMF. The DTMF signal is fed into the normal audio input of the GSGC9 which intercepts and decodes the instructions. To use the GSGC9 it is therefore essential to be able to provide the correct DTMF tones. Glensound make several DTMF dial units especially for this equipment.

The GSGC10 is our simplest dialler. This hand held battery operated unit has its output on two bantam jacks, one at line level and one at mic level in addition to an acoustic output so that it can be used by holding it close to a microphone.

Other controllers are our GSGC12 designed especially for our coaxial commentators boxes, and our GSGC13 unit which fits in the 3U subrack to provide a simple method for local control.

Information about the call, or the set up is provided to the user by recorded messages. These appear on the normal codec output circuits so they can be monitored on a typical studio monitoring system or any loudspeaker. A very small loudspeaker is provided in the GSGC13 dialler module.

To prevent inadvertent messages being heard on air it is possible for the operator to select full or just essential messages.

With a 3U subrack (with GSGC9 modules) installed in an apparatus room it is only necessary to feed the audio inputs and outputs to the studio control room. The dialling and monitoring can then be performed from the studio because all signals are in band. No additional control circuits are required.

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