ELD-1 Front
Speaker Line Connecter
A plug-in barrier-strip connector on the ELD-1 connects the device to the end of the speaker line. The
device needs to be connected to an appropriate monitoring point on the speaker cable—typically after the
last speaker on the run. Connect the speaker line between the Com pin and the appropriate Low or High
pin.
Speaker Circuit
Amplifier Power
Less than 100W 100W or greater
4
Ω
Low
Low
6
Ω
Low
Low
8
Ω
Low
Low
25 Volt
Low
Low
70 Volt
Low
Low
100 Volt
Low
High
Note that for circuits connected to the Low terminal the ELD-1 presents a 0.5 Watt load to a 70V circuit
and a 1 Watt load to a 100V circuit.
Output Fault Detection
The Amplifier monitors (supervises) for faults on speaker connections using a combination of multiple out-
of-band (inaudible) high frequency tones.
For end-of-line detection, one or more (up to 15 maximum) ELD-1 units can be connected to the speaker
line. To ensure correct operation of fault detection it is necessary to follow these guidelines:
•
Recorded audio messages or audio content with continuous or swept tonal components (e.g. alert
tones) and any content with significant high frequency harmonic content should be band limited
(>24dB/octave) at 15 kHz during recording. Note that program content that is distorted due to poor
recording techniques may contain excessive high frequency harmonics.
•
Signal level adjustments within a Vocia system should be set so as to minimize clipping. Severely
clipped signals may also affect the out-of-band fault detection tones.
•
The use of speaker cables that inherently attenuate high frequencies is not supported (e.g. screened
cables). Speaker cables must maintain frequency response to the end of line of less than -3dB @
20kHz at with respect to 1kHz.
•
Speaker cables longer than 500 feet may prevent correct operation of ELD and Ground Fault
monitoring capabilities. An advantage of Vocia is that amplifiers may be easily distributed close to
speakers, thereby minimizing long runs of expensive and potentially lossy speaker cable.
•
Highly capacitive speaker lines or loads may prevent correct operation of the ELD detection system.
•
Legacy monitored speaker circuits that use capacitors and resistors or similar methods must have all
legacy monitoring circuitry removed for correct operation of the ELD detection system.
•
For EN 54-16 compliance, one or more ELD units must be fitted. End of Line detection must be
enabled in the Vocia software.
