H HEUER INSTRUMENTS - Applications [Home Page]

Automatic Loss Measurement(ALM) to R41

Commissioning Tests on 2 Wire Voicelinks

Commissioning Tests on 4 Wire Voicelinks

Automatic Loss Measurement (ALM) to R41 [Top]

R41 in 'Auto Answer' mode
R41 in 'Customer Equipment' mode
Additional measurements in ALM mode

Return Loss
Impulse Noise
Dropout
Level Recorder

R41 in 'Auto Answer' mode [Back]

The R41 answers the call and releases the line at completion of the test sequence


Figure 1: Loss measurements in Auto Answer mode

  1. Connect the Responder R41 line socket to the remote END B, set to Auto Answer.
  2. Connect the LM41 to the line at END A and press On-Off
  3. Press ALM and enter the Tel number
  4. Press Dial - the Responder R41 answers the call
  5. Take the following readings:
  6. At any time press Dial to select optional 13 frequencies
  7. Press save to store one cycle of ALM results
  8. Press ALM twice to disconnect

Note: The 3 kHz bandpass filter in the LM41 has 3 dB attenuation at 300 Hz and at 3.4 kHz. The bandpass filter in the R41 has 3 dB attenuation at 90 Hz and 4 kHz approximately

R41 in ' Customer Equipment' mode [Back]

The Customer Equipment answers the call


Figure 2: Loss measurements in Customer Equipment mode

  1. Connect the Responder R41 line socket to the remote END B, set to Customer Equipment
  2. Connect the customer equipment to the R41
  3. Connect the LM41 to the line at END A and press On-Off
  4. Press ALM and enter the Tel number
  5. Press Dial - the Responder R41 will disconnect the CE and connect the Responder R41 to the line
  6. Take the following readings:
  7. At any time press Dial to select optional 13 frequencies
  8. Press save to store one cycle of ALM results
  9. Press ALM twice to disconnect

Additional Measurements in ALM mode [Back]

Setup as for above tests
After establishing connection with the R41 it is possible to commence any of the following tests:

Return Loss [Back]

  1. Press Return Loss
  2. Press Dial to toggle 3 or 13 spot frequencies
  3. Take the following readings

Impulse Noise [Back]

  1. Press ImpNoise
  2. Press ImpNoise again to start the measurement with default settings

  3. Otherwise:
    Press Dial to set the level threshold and then press Enter
  4. Press Dial twice to set the duration and then press Enter
  5. Press ImpNoise to start the measurement
  6. Press ImpNoise again to stop the measurement
  7. Press save to store Impulse Noise results

Dropout [Back]

  1. Hold down the ImpNoise button, the Responder R41 sends a tone back.
  2. Press ImpNoise again to start the measurement with default settings

  3. Otherwise:
    Press Dial to set the level threshold and then press Enter
  4. Press Dial twice to set the duration and then press Enter
  5. Press ImpNoise to start the measurement
  6. Press ImpNoise again to stop the measurement
  7. Press save to store Impulse Noise results

Level Recorder [Back]

  1. Press Level *
  2. Hold down the Enter button until " Recorder time " appears
  3. Press Enter again to start the measurement with default settings

  4. Otherwise:
    Press Dial to set the recorder duration then press Enter, this starts the measurement

Recorder results are saved automatically.
The recorder terminates when the time expires or when any button is pressed.
* Note: It may be advisable to set a suitable fixed range manually to avoid possible switching transients whilst recording. Hold down the Dial button until "Manual range" appears and then select the range.

Commissioning Tests on 2 Wire VoiceLinks [Top]

Test 1 Link Transmission Loss and Slope
Test 2 Ring Current Continuity
Test 3 Loop Current
Test 4 Speech Quality Test
Test 5 RATES Test

Test 1 Link Transmission Loss and Slope in ALM mode [Back]


Figure 3: Test Setup for Telephone Tests

  1. Connect the Responder R41 line socket to the remote END B, set to On Line
  2. Connect the Feedbridge FB41 line output to END A
  3. Press ALM twice on the LM41, "ALM"
  4. Press FB41/4W twice on the LM41, "2wire FB ON"
  5. Take the following readings:

Note: The 3 kHz bandpass filter in the LM41 has 3 dB attenuation at 300 Hz and at 3.4 kHz. The 4 kHz bandpass filter in the R41 has 3 dB attenuation at 90 Hz and 4 kHz approx.

Test 2,3,4 Telephone Tests [Back]


Figure 4: Test Setup for Telephone Tests

Ring Current Continuity [Back]

  1. Connect the Feedbridge FB41 to the line at end A. Connect an LM41 to the line at end B
  2. Set the LM41 (B) to TEL and read the DC line voltage. Press the Ring button on the feedbridge
  3. The LM41 (B) should ring, record the Ring voltage

Loop Current [Back]

Press Tel again on the LM41 (B) and read the loop current. It must be > 20 mA.

Note: Where signalling repeaters, Interface Units or SSN MUX are used, there are two current loops in the link. When measuring current at the A End place an ammeter at the A End in series with the FB41. This current must be > 18 mA.

Speech Quality Test [Back]

The objective is to verify that the speech quality is subjectively satisfactory with respect to "hollowness" (echo) and noise/hum level. A subjective test is considered adequate in the great majority of cases.

Press Tel twice to set the LM41 (A) to "TEL on line".

Use the handsets to assess link speech quality.

Test 5 RATES Test [Back]

The objective is to verify that the RLTU or the RLT4 remote test facilities are functioning correctly.


Figure 5: RLTU in 2 Wire Idle State

RLTU Operation

  1. When the RLTU is powered, the green power LED will be on, with the tone detection circuitry ready to commence the "tri-state" test sequence, as shown in Figure 5. In the idle state, and under RLTU power fail conditions (green LED off), the transmission path is connected through to the CE.
  2. Press the RLT4 button on the LM41 to enter the RLTU interface mode. Pressing RLT4 again applies a 2700 Hz tone for >5 s. The RLTU responds by isolating the CE and sending back 820 Hz tone at -10 dBm. The LM41 measures the received line level and displays the RxLoss (i.e. a -16 dBm line level corresponds to a 6 dB loss). The red test LED will come on, as shown in Figure 6. If there is no response, ask the customer whether the green Power LED is on before continuing your investigation.
  3. Pressing RLT4 again reapplies the 2700 Hz tone. The RLTU in 2 Wire mode applies a 600 ohm resistive termination to the line, to allow noise tests or return loss measurements, as in Figure 7.
  4. Pressing RLT4 again reapplies the 2700 Hz tone for the third time, and the units will return to idle, as shown in Figure 5. The RLTU includes an automatic 5 minute reset timer and a local push button switch which can also be used to return the unit to its idle state.


Figure 6: RLTU in 2 Wire, 820 Hz Return State


Figure 7: RLTU in 2 Wire Line 600 Ohm Terminated State

Test Procedure

  1. Connect the Feedbridge FB41 line output to END A
  2. Press FB41/4W twice on the LM41, "2wire FB ON"
  3. Set the LM41 to RLT4 interface mode
  4. Press RLT4 again, read the RxLoss (RLTU in 820 Hz Return State)
  5. Press RLT4 again, read the psophometric and 3 kHz bandpass noise (RLTU in Terminated State)
  6. Press RLT4 again, this will reset the RLTU

Commissioning Tests on 4 Wire VoiceLinks [Top]

Test 1 Speech Quality Test
Test 2 Link Transmission Loss and Slope
Test 3 E & M Lead Operation
Test 4 RATES Test


Figure 8: Test Setup for 4 Wire Links

Speech Quality Test [Back]

The objective is to verify that the speech quality is subjectively satisfactory with respect to "hollowness" (echo) and noise/hum level. A subjective test is considered adequate in the great majority of cases.

  1. Set the LM41 to Tel "off line"
  2. Select "4wire" with 4W button - display shows: " 4W Telephone"
  3. Use the handset to communicate

Link Transmission Loss and Slope [Back]

See Figure 8

  1. Set the LG41 to -10 dBm, 820 Hz and connect to the A end. At the B end check that the LM41 reading, 600 W terminated is: -9 dBm to 11 dBm
  2. Repeat with 3 kHz and check that the reading is at most ±1 dB different to that at 820 Hz
  3. Repeat tests 4 and 5 in the opposite direction

If all measurements are within tolerance, proceed to the signalling tests.

E & M Lead Continuity [Back]


Figure 9: Test Setup for E&M Continuity

  1. Connect a Feedbridge FB41 each to End A and End B of the link. An earth lead from the frame must be connected to each FB41 for this test.
  2. At end A, Set the M-switch towards the LED, this places an earth on the M lead. Check that the M-LED turns on. At end B, check that the E-LED turns on. This condition is shown in Figure 9.
  3. At end B, Set the M-switch towards the LED, this places an earth on the M lead. Check that the M-LED turns on. At end A, check that the E-LED turns on

RATES Test [Back]


Figure 10: 4 Wire RLTU in Idle State

The objective is to verify that the RLTU or the RLT4 remote test facilities are functioning correctly.

RLTU Operation

When the RLTU is powered, the green power LED will be on, with the tone detection circuitry ready to commence the "tri-state" test sequence, as shown in Figure 10. In the idle state, and under RLTU power fail conditions (green LED off), the transmission path is through connected to the CE.


Figure 11: 4 Wire RLTU Responding with 820 Hz

When the RLTU receives 2700 Hz for 5 seconds or longer it will respond by isolating the CE and sending back a 820 Hz tone at -10 dBm. The red test LED will come on, as shown in Figure 11. If there is no response, ask the customer whether the green POWER LED is on before continuing your investigation.


Figure 12: 4 Wire RLTU in 6 dB Loopback Mode

Reapplying the 2700 Hz tone for 5 seconds or longer set the RLTU into loopback mode with 6 dB loss.

Reapplying the 2700 Hz tone for the third time for 5 seconds or longer, will return the RLTU to idle, as shown in Figure 12. The RLTU includes an automatic 5 minute reset timer and a local push button switch which can also be used to return the unit to its idle state.

Test Procedure

  1. Set the LM41 to RLTU by pressing the RLT4 button
  2. Select "4wire" with 4W button - display shows "4W" in bottom RH corner
  3. Press RLT4 again to start the measurement and read the Rx-Loss at 820 Hz (RLTU in 820 Hz Return State)
  4. Press RLT4 again, this sets the RLTU into loopback mode. (RLTU in 6 dB Loopback Mode). Read the Tx-Loss at 820 Hz
  5. Press RLT4 again, this will reset the RLTU