Frequently Asked Questions

Readings Fail when Phone Line Attached

The system operates normally in both local and remote operation until the telephone line is attached. All telemetry readings become zero or status off.

This indicates an interaction with the telephone line. The RFC-1/RAK has both transformer and optical isolation from the telephone line. Despite this, there are some potential issues.

Sometimes the condition is caused by a damaged telephone line and sometimes the RAK-1 introduces the problem. While testing, it is best to bypass any external devices or surge suppressors to isolate if the RAK-1 is the source of the problem.

Telephone Connector Test

The telephone connector sits very close over the rear panel of the chassis. The shape of the metal extrusion that supports the chassis creates a potential condition. The connector leads are trimmed very short so that the connector does not short against the chassis.

Occasionally the board sags a little over time and the connector leads make intermittent contact with the chassis. It is rare but it can happen. The test is simply to turn the unit upside-down and test it.

If the system works normally while upside down then one of the telephone connectors probably touching the chassis. The easy field repair is to insulate the critical spot with black electrical tape.

1. Disconnect all cables from the RAK-1 and remove it from the equipment rack.
2. Disconnect the backup battery using the rear switch.
3. Remove the two philips screws from the rear edge of the top cover and slide the cover out of the chassis.
4. Remove the jackscrews from the parallel printer port.
5. Remove the rear panel from the RAK-1 by removing the two philips screws from each side.
6. Make sure that the leads to the telephone connector are cut flush to the board.
7. Apply two layers of black electrical tape to the board at the underside of the telephone connector. This provides enough insulation so that there is not contact when the device is reassembled and turned right side up.
8. Reassemble the unit by replacing the pieces in the reverse order that they were removed.
9. Apply power to the RAK-1 and test.

Telephone Line Polarity

Telephone lines and devices connected to them are not supposed to be polarity sensitive. But sometimes it is that easy. Swap the polarity of the telephone line and test to find out if the situation improves.

Bypass the RAK-1 Telephone Circuitry

To determine if the RAK-1 circuitry is introducing the problem, bypass the RAK-1 telephone circuits. This is not nearly as invasive as it may sound because there are internal modular connectors on the RFC-1/B.

1. Disconnect all cables from the RAK-1 and remove it from the equipment rack.
2. Disconnect the backup battery using the rear switch.
3. Remove the two philips screws from the rear edge of the top cover and slide the cover out of the chassis.
4. Inside the chassis there are two short (2 inch) silver satin cables terminated in RJ-11 connectors that attach to the RFC-1/B. Disconnect both modular connectors.
5. The modular connector that is closest to the front of the RAK-1 is the telephone line. Insert the telephone line to that connector and insert the local phone in the remaining connector.
6. Apply power to the RAK-1 and test. If the condition persists then the RAK-1 is not likely to be causing the problem.

Ring Indicator LED

A small percentage of telephone lines do not like the RAK-1 ring detection circuit used on board revision 5A and earlier. Reversing the line polarity will correct this most of the time. If it does not, the only remaining option is to disable the ring indicator LED.

1. Disconnect all cables from the RAK-1 and remove it from the equipment rack.
2. Disconnect the backup battery using the rear switch.
3. Remove the two philips screws from the rear edge of the top cover and slide the cover out of the chassis.
4. At the front of the RAK-1 to the right of ring indicate LED there are three components: transistor Q2, diode D14 and resistor R6. Lift one leg of either the resistor or diode to break the signal path.
5. Reassemble the unit by replacing the pieces in the reverse order that they were removed.
6. Apply power to the RAK-1 and test.

This is the most invasive procedure discussed but it is also very easy to undo. The LED will not function but it is better to have accurate telemetry.