Loudspeaker Line Monitoring - DC
From Zenitel Wiki
DC End-of-Line (EOL) monitoring uses a 10 kΩ resistor fitted at the end of a loudspeaker line.
The 10 kΩ resistor is utilised by the Amplifier Frame, which applies a small DC monitoring current across the loudspeaker line circuit, then measures the resistance. This in turn, allows the Amplifier Frame to continuously monitor the integrity of the circuit.
Typical example values you should expect to see in a single circuit:
- Healthy line: approximately 10 kΩ is detected.
- Open circuit (cable break or missing EOL resistor): resistance becomes very high or infinite.
- Short circuit: resistance falls to a very low value.
- Earth leakage or wiring faults: the measured resistance changes outside the permitted tolerance, generating a fault.
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| EOL Topology Example |
Key Points
- Simple and reliable.
- Cost effective.
- Commissioned in the ADT (Amplifier Dynamic Tool) of the SCT (System Configuration Tool).
- Allows Up to 10 End of Line spurred circuits per Amplifier Frame.
- Unaffected by cable capacitance and presence of audio.
- Does not use signalling down cable screen.
- Compliant to EN54-16.
- Resistor is 10K 3 watt 1% with high temperature stability.
- We recommend Zenitel sourced EOL10K's are used to mitigate spurious faults.
"DC Blocking" Capacitor Information
All loudspeakers connected to the system must be fitted with "DC Blocking" capacitors. Loudspeakers are available with suitable capacitors pre-installed from a variety of suppliers. Alternatively, blocking capacitors may be retro-fitted. The following range of kits are available your Zenitel Stockist:-
| Maximum Loudspeaker Power Rating (Power Tapping - W) | Zenitel Part Name | Zenitel Part Number | Capacitance Value (uF) |
| 2 | LBC2W-10PACK | 1200530002 | 0.33 |
| 6 | LBC6W-10PACK | 1200530006 | 1 |
| 14 | LBC14W-10PACK | 1200530014 | 2.2 |
| 30 | LBC30W-10PACK | 1200530030 | 4.7 |
| 63 | LBC63W-10PACK | 1200530063 | 10 |
If alternative capacitors are to be fitted, they must be non-polarised and rated to at least 250Vdc and 160Vac. Polyester sealed case types are recommended.
The capacitance values listed above will provide negligible attenuation of (-3db) at 100Hz. If improved low-frequency performance is required, the "DC Blocking" capacitors may be increased in value. Doubling the value will halve the "-3dB" frequency.
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| "DC Blocking" Capacitor Placement |