Toa SX-2000 Series Installation - Manual (Page 134)

134
4.8. Connections to Use the Surveillance Function
4.8.1. Speaker line surveillance (SX-2100AO only)
the speaker line surveillance function detects 3 types of failures: poor insulation (ground fault), overload (line
short), and cable disconnection.
for detecting both overload and cable disconnection, use the method that detects such failures by monitoring
the impedance in a speaker line (referred to as Impedance method).
Particularly to improve the accuracy of detecting cable disconnection, use the method that detects cable
disconnection by connecting an End-of-line (Eol) unit at the end of speaker line (referred to as Eol method).
features of each method are shown below.
(1) Impedance method
• Applies to various types of speaker cables (no need to use shielded type cables).
• Needs no additional detector to be connected to the speaker line.
• Provides less precision in detection of speaker cable disconnection than the EOL method.
(2) EOL method
• Detects speaker cable disconnection precisely.
• Needs shielded speaker cables to be used.
• Needs an EOL unit to be connected to the speaker line.
[general description of the Impedance method]
the speaker impedance is stored in the SX-2100Ao after measured with a pilot tone signal of low frequency.
the SX-2100Ao continuously observes the speaker line impedance, and compares it with the stored value to
judge overload or disconnection of the speaker line.
the speaker line impedance may fluctuate even in normal state with the influence of impedance variations
caused by the speaker's impedance change, broadcast signal frequency difference, and ambient temperature
change. In such cases, the detection sensitivity can be adjusted. (See p. 140, "Speaker line Initial Setting." )
In an application that many low power speakers are connected to an amplifier with high power output, the
impedance variation stays within the measurement tolerance even if one speaker is disconnected, disabling the
detection of speaker cable disconnection. In such cases, adjust the detection sensitivity of cable disconnection
or select the Eol method.
SX-2100AO
Ground fault
detection
Short/open circuit detection
through impedance detection
SP
AMP
PA LINK
40 Hz
Pilot Tone