faq


 
By Application
By Product
7501-15 (Plug-in DC Trip/DC Pilot Wire Card)
7501-72 (Plug-in Two-Wire AC Data Card)
751109/13 (Eight-Card Shelf)
751221 (Standalone Telephone Unit)
751321 (Plug-in Expandable Telephone Card)
751329 (Plug-in Four-Wire T1 Carrier Card)
751333A (Plug-in ISDN plus 56K Adtran Card)
751339 (Plug-in Four-Wire HDSL Card)
On Installation
» Why is there approximately 2 mA more on the station side than on the CO side?
» How often should the calibration procedure be performed?
» While trying to do a field calibration, what should be done if the mentioned currents in the procedure cannot be obtained?

 

Why is there approximately 2 mA more on the station side than on the CO side?
To remove ground imbalance circuit. The extra current on the CO side is drawn by the ground imbalance circuit.

If the ground imbalance detector is not required, the circuit can be easily be removed on newer revision of cards. On older revisions, the card can be sent to Positron to implement Modification Bulletin #7501-15-39.

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How often should the calibration procedure be performed?
The field calibration procedure should be performed once after the first year and once after the second year to compensate for aging components. Then, it should be performed once every two years.

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While trying to do a field calibration, what should be done if the mentioned currents in the procedure cannot be obtained?
This occurs when the card needs a more thorough calibration. A bench calibration procedure should then be performed, as shown in the manual. If after this, it is still not possible to obtain good readings, the card should be sent to Positron for a complete adjustment.

When the circuit does not work, do the following before calling Positron, in order to speed up the resolution of the problem:

** Resolution of a problem is made easier with a 751366 line test card. It is recommended to have one per site to make measurements easier. If you do not have one, troubleshooting is still possible, but more difficult for the technician.

1. Measure the loop current on the unit’s station and CO side; they should be about the same (±10%). If there is no current, make sure the supply voltage is right for that model (A = 130Vdc, B = -24 Vdc, C = -48 Vdc floating).

2. Measure the voltage on the unit’s station and CO side; they should be about the same (±10%).

3. Make sure you have a good connection to the CO ground on the RMT GND of the CO cable.

4. Measure the level of common mode on the CO side. This is measured using a multimeter between Tip and RMT GND, and then between Ring and RMT GND. If there is more than 4 V of common mode (60 Hz), the ground imbalance detector circuit might be affected and may cause malfunction of the card.

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