Bosch PRAESENSA PRA-EOL End-of-line device

• Compact device for loudspeaker end‑of‑line supervision
• Reliable solution for (long) loudspeaker lines
• Fault detection in amplifier without additional wiring
• Low level, high frequency pilot tone
• Flexible mounting options

This end‑of‑line device is a reliable solution for loudspeaker line integrity supervision, which is a requirement for emergency sound systems. It is connected at the end of a loudspeaker line, after the last loudspeaker of a series of looped-through loudspeakers.
It communicates with the PRAESENSA amplifier channel driving that loudspeaker line, to confirm the integrity of the line. Where impedance measurements may not detect a disconnected loudspeaker, depending on the number
of connected loudspeakers and cable type, or report false faults, the end-of-line device provides a superior solution to report the correct status of the loudspeaker line.
The enclosure size is compatible with the mounting provisions in most Bosch loudspeakers for supervision boards or devices. It can also be reduced in size to fit most cable junction boxes.

Functions
Supervision

• Reliable supervision of a single loudspeaker line, using loudspeakers connected in a loop‑through fashion.
• Operation is based on pilot tone detection from the amplifier with feedback to the amplifier using the loudspeaker line itself. No additional wiring is needed for fault or status reporting.
• The A/B outputs of a PRAESENSA amplifier channel are supervised individually, with separate end‑of‑line devices.
• To reduce power consumption, PRAESENSA amplifier channels use pilot tone modulation.
• The audibility of the pilot tone is virtually eliminated by using a pilot tone amplitude of only 3 VRMS with a frequency of 25.5 kHz, amply outside the human hearing range, even for young children.

Mounting

• The PRAESENSA end‑of‑line device is small, lightweight and fits to the mounting provisions in most Bosch loudspeakers for supervision boards (board shape). It comes with push terminal connected flying leads, containing a thermal fuse, for easy connection to the last loudspeaker of a loudspeaker line.
• Part of the mounting plate of the device can be broken off and snapped in place as bottom plate, making the device enclosure IP30 compliant, for use outside a loudspeaker enclosure (box shape). The enclosure contains a wiring strain relief for additional protection.
• Various mounting holes in the enclosure allow for mounting the device in most standard cable junction boxes. In this case the loudspeaker line enters the box via a standard cable gland and is connected using the push terminal.