F.M. MONITORING RACK

Model No.: TW/FM/MON RACK

Input and Monitoring Rack is designed to feed stereo programmes for FM Stereo broadcasting. This accepts stereo program signals that come from studio, processes the audio signal to the required nominal level with professional quality and feeds it to the Transmitter. Apart from processing the input signal fed to the Transmitter, this rack provides the facility of monitoring all stages.

The monitoring is done by

Stereo Audio Amplifier & External Speakers for aural monitoring
Stereo VU meter with 2 channels of 40 LEDs each for visual monitoring.

The Input and Monitoring Rack is assembled in EIA standard 19" Rack with the same height as the FM Transmitters that are already in AIR network One set of the following units is assembled in the rack as shown in the enclosed front view.

VU Meter Assembly
Stereo Audio Switcher 6 Way
Audio Stero Patch Panel Assembly
Stereo Audio Switcher 3 Way
Line Amplifier Assembly
Monitoring Amplifier Assembly
MCB Panel Assembly

Important points in the Programme and Monitoring chain has been brought to a stereo jack panel consisting of 24 twin jacks in two rows.

The Input and Monitoring Rack works on 230 V AC, 50Hz Mains Supply and dc Power supply is not used . Each unit has its own RFI filter and Power Supply unit. Input and Output Audio signals to / from the rack is given through a connector panel mounted at the bottom rear side of the rack . The MIL standard approved, PTFE insulated, 2 core audio cables are used for the rack wiring.

Brief descriptions of the Sub units are famished below.

(1.) 3 Way Audio Selector

The 3 way Audio Selector has three balanced stereo inputs

Specification
No. of Inputs	3 Stereo inputs
No. of Outputs	I Stereo output
IN / OUT Isolation	90 dB
IN / IN Isolation	90 dB
Input Level	+20 dB (max); +6 dB(nom)
Input Impedance	600 0 balanced
Output Impedance	600 0 balanced
Distortion	< 0. 1 % (40 Hz - 15 kHz)
Cross Talk	> 85 dB
S / N Ratio	> 85 dB
Phase Difference	<3Degree
Power Supply	230 V, ±10%, 50 Hz Mains

(2.) VU Meter

Specification
Input Level	-37 dB to -10 dB in 3 dB steps +20 dB to -10 dB in I dB steps
No. of Display LED	40 in 3 colors per channel
Input Impedance	> l0kQ
Display stages	1. -37 dB to -6 dB (3 dB steps) - Green 2. -5 dB to +5 dB (I dB step) - Yellow 3. +6 dB to +20 dB(I dB step) - Red
Tolerance	± I LED (0.5 dB)
Dimensions	I U (Height), 19"
In Put Power supply	230 V, AC +/- 10%, 50 Hz Mains

(3.) 6 Way Audio Selector

The 6 way selector has high input impedance > 10k and hence it will not load the point of monitoring.

Specification
No. of Inputs	6 Stereo inputs
No. of Outputs	I Stereo output
Input Impedance	l0k 0
IN / OUT Isolation	90 dB
IN / IN Isolation	90 dB
Input Level	+20 dB (max)
Distortion	< 0. t % (40 Hz - 15 kHz)
Cross Talk	> 85 dB
S /N Ratio	> 85 dB
Phase Difference	< 3o
Power Supply	230 V, ± 10%, 50 Hz Mains

(4.) Stereo Line Amplifier

Specification
No. of Inputs	2 (1 L+ I R)
No. of Outputs	2 (1 L+1R)
Input Impedance 1	600 Q balanced
Output Impedance	< 50 Q balanced
Audio Input Level	- 6 dBm to + 20 dBm
Audio Output Level	0 dBm (nominal), +20 dBm (rnax)
Frequency Response	± 0.5 dB
Distortion	< 0. 1%
Cross Talk	> 80 dB
S/N Ratio	> 80 dB
Phase Difference	< 3 o
Power Supply	230 V, ±1 0%, 50 Hz Mains

(5.) Audio Jack Panel

The Audio Jack Panel is designed for bypassing or interconnecting different stages in Audio Chain . This patch panel also provides facility for connecting headphone to monitor a stage in the audio chain without loading the port . All audio connections are using twin socket so that it is compatible for stereo operation.

Specification
No. of Jacks	48 (24 stereo)
Spring Material	Solid Nickel Silver
Contact resistance	< 0.015 0
Working Voltage	100 V dc
Material	Palladium

(6.) Monitoring Amplifier

The stereo Monitoring Amplifier contains two identical, hi fi Audio Amplifiers . The Monitoring Amplifier has 3 modes of operation; Dual Mono, Stereo and Bridged Mono.

Additional Features

The Monitoring Amplifier provides a selectable low pass / high pass filter. The selection is done using a front panel switch.
This unit is capable of working independently on 230 V AC Main supply. The audio input to the unit is fed through XLR (I L & I R) connectors and the output is available as low impedance at a terminal block provided at the side. Proven discrete power devices used are mounted heat sinks with thermostat protection.

Specification
No. of Inputs	2 (IL+IR)
Outputs	40W rms
Input Impedance	>10 k 0 balanced
Output Impedance	8 0
Audio Input Level	- 10 dBrn to + 10 dBm
Frequency Response	± 0.2 dB (40 Hz - 15 kHz)
Distortion	< 0.2% at I kI-Iz
C-TOSS TZAV	> W dB
S IN Ratio	> 80 dB
Phase Difference	<3'
Power Supply	230 V, ±10%, 50 Hz Mains