Noise Control & System Protection

Introduction

With the increasing demand for stricter fire and noise control regulations, Formula Sound have often been asked to "provide something that meets the requirements".

During consultations with Fire Officers, the brief which evolved required that, in order to avoid panic when a fire alarm activates, the programme level in the venue should be reduced and not cut altogether, and that a mic override facility should provide one guaranteed microphone into the system.

In the firm belief that regulations will become even tighter the company felt that it was time to develop a unit that would satisfy all these requirements but would also serve other uses. So Formula Sound have developed and produced the Guardian CX4.

The unit is not restricted to entertainment venues and may be used with any sound system where a priority override facility is required. It is ideal for use in shopping centres, malls and public areas where security announcements are required. Priority inputs may be at mic or line level.
This unit will interface with any existing or new sound installation. It is a four channel device and has two distinct functions.

Priority Override

The Guardian has been designed to be connected between the mixer (or pre-amp) of an audio system and the power amplifiers. The unit may be connected to 4 channels of audio, normally 2 stereo pairs. The priority inputs (e.g. DJ microphone) is connected to the priority input socket. This may be at mic or line level (as selected by internal switch).

The control input is connected to the fire alarm or whatever triggering method has been decided. When the unit is triggered, the programme level in all four channels will be attenuated and the priority input automatically mixed into all four outputs. Four controls are provided - 2 controls to set the attenuation level of channels 1-2 and 3-4; 2 controls to adjust the priority input level into channels 1-2 and 3-4. These are only accessible by removing the security front panel. Test and reset buttons, operational though small holes in the front panel are provided for initial setting up and testing.

Reset

Two modes of reset, auto and manual are determined by the reset button. This is a latching push button, the position of which sets the reset mode. If left in the out position, reset will be manual. That is to say, when the control signal is removed the unit will not reset until the reset button is depressed. If the button is left in the depressed position, the unit will automatically reset when the control signal is removed. When the unit is reset the programme will fade slowly back to the original volume.

Balanced inputs and outputs are provided which may be strapped unbalanced with no signal loss and optional transformers may be fitted.

Noise Limiter

The Guardian CX4 also has the provision for controlling the maximum permitted volume level. This is often necessary when having to conform to noise pollution requirements. The operation is quite simple. The unit monitors the level in channels 1 and 2, and if this combined level exceeds an internally set threshold a warning lamp illuminates. If the level is reduced, no action is taken. If the lamp is illuminated continuously for 6 seconds the limit will be activated. This turns the programme level down to the attenuated level - as set by the attenuation controls, for approximately 10 seconds and has a 10 second fade back time. The unit will keep returning to the attenuated level until the operating level is reduced to below the threshold. Limit may be disabled by adjusting the internal threshold preset to a sufficiently high level.

LED indicators of warning, limit and priority are on the front panel and an output socket is provided on the rear for remote indicators.