AD 903 2 Wire to 4 Wire Adapter
1 CONNECTING THE STATI0N TO THE SYSTEM
Connections from the external system to the AD 903 are made via the 4-pin XLR type connector as follows: -
Output FROM external 4 wire system PIN I Low
PIN 2 High
Input TO external 4 wire system PIN 3 Low
PIN 4 High
Both connectors are transformer isolated and floating.
If using balanced feeds, connect phase to "high". Do not connect screens, even to each other, and ensure that they are grounded at the external equipment.
If using unbalanced feeds, connect signal to "high" and screens to "low". Do not connect screens together, in order to avoid ground loops, do not make any connections to the chassis of the AD 903 unless there are no other ground connections to the external system. If grounding is required, use only one of the screens.
The rest of the Technical Projects system is plugged in via the 3-pin XLR type connectors and this is fed back through the outstations to a master station or power supply.
2 BASIC OPERATION
The levels of the external system to and from the Technical Projects system are set as follows: -
The screwdriver preset controls the output from the 4 wire system and attenuator switch marked "Output". If the signal is insufficient even with the preset fully clockwise put the switch to "Lo" and re-adjusts the preset.
The screwdriver preset controls the input to the 4 wire system and attenuator switch marked "Input". If the signal level is insufficient even with the preset fully clockwise put the switch to "Hi" and re-adjusts the preset.
When connected to other talkback systems there may be sidetone - a portion of the output being heard on the input - provided on that system. This must be set to zero or as low as possible and then any sidetone required can be provided by turning the "Null" screwdriver preset on the AD 903.
Any sidetone created other than in the AD 903 will cause the bridging impedance of the adapter to reduce which can cause the sidetone balance throughout the 2 wire system to be altered. In extreme cases this can prevent satisfactory operation altogether.
Connection to 3 wire systems (4 wire with common return-screen) must be done using the shortest possible cable between the AD 903 and the 3 wire connector.
Last Modified : 09 February, 2006