Radio Receiver/Transceiver (Option); Local Microphone Input And Volume Control; System Diagnostics; Power Amplifier Operation - Whelen Engineering Company IPS 400 Product Manual

The ESC-864 board reports status information to a central control point in response to the following alarm conditions:
- a change-of-state alarm (user selectable on/off)
- instant response to individual activation (user selectable on/off) or
- response to individual interrogation.
In the event of an alarm condition, the ESC-864 board will transmit its status report three times to ensure that the
message is received. The first transmission will happen immediately upon change of status, the second transmission
fifteen (15) seconds after the first, and the third fifteen (l5) seconds after the second transmission. If, after these
transmissions, the RF link remains busy, the ESC-864 PC board will terminate transmission. With respect to this latter
statement, a squelch detect circuit is included within the ESC-864 board's design. This feature prevents interference with
other transmissions on the RF link. The squelch detect circuit will not transmit status information if the RF channel is
busy, and it will wait for a clear channel prior to transmitting. The ESC-864 may be configured to operate in the squelch
detect mode on the basis of noise squelch or tone-coded squelch.
The ESC-864 board provides service and diagnostic information concerning its radio receive link upon initiation of a
diagnostic sequence from the central control point by an E-864/M Encoder and Status Display. In response to carrier-
only and tone sequence, the ESC-864 PC board examines its receive signal-to-noise ratio and transmits this information
back to the central control point.

4.1.7 Radio Receiver/Transceiver (option)

The radio receiver/transceiver is typically installed in the ESC-864 housing. The radio receiver/transmitter option is
available at low band VHF (30-50 MHz), high band VHF (150-170 MHz), or UHF (450-470 MHz).

4.1.8 Local Microphone Input and Volume Control

The local microphone controls are mounted on the front panel of the ESC-864 housing, to allow the user to plug in a
microphone to access the public address channel of the IPS. While it may be obvious that the microphone plugs into the
jack, and that the microphone volume control knob allows for adjustment of the output level, a clipping indicator above
the microphone volume control knob is provided to indicate the distortion level of the microphone. During PA, the
clipping indicator should be flickering on and off (i.e., operating at minimal illumination levels).

4.1.9 System Diagnostics

All IPS systems are equipped with diagnostic capabilities. The diagnostics provide a basic summary of the system
operations concerning AC power, DC power, speakers, and power amplifiers. As previously described, the information
from the diagnostics is presented by the various LEDs on the front panel of the ESC-864 housing.

4.2 Power Amplifier Operation

The power amplifiers are located on the backside of the front panel of the IPS. As previously stated, one 400 W power
amplifier is used in an IPS-400, while an IPS-800 is equipped with two power amplifiers. Each power amplifier has four
(4), 100 W speaker channels, for a total of 400 watts per amplifier.
Each power amplifier is powered by 24 VDC. The amplifiers are hard-wired to the system driver board. Each power
amplifier is protected by a 30 Amp fuse, near its connectors. The failure of one amplifier does not cause the failure a
second amplifier; however, all four power amplifier channels within a faulty power amplifier will fail in the case of a
blown fuse.
Each power amplifier is mounted on the backside of the front panel so that four (4) red LEDs are visible (on the front
side of the front panel), one for each 100 W channel of each power amplifier. These LEDs are used to monitor the
11