Microphone multiplex system accepts an audio signal from a single source and provides any number of low impedance outputs at microphone level with complete isolation between output channels. Any input or output may be converted to high impedance by eliminating the associated transformer

Lauver, R. E.

English

NASA Technical Reports Server

August 1966 l"_1c
	
Brief 66-1.0308 
NASA TECH BRIEF A	 11 
NASA Tech Briefs are issued to summarize specific innovations derived from the U. S. space 
program and to encourage their commercial application. Copies are available to the public from 
the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
- 'iI	 a_i. ITiiT	 TTiii	 .iTrTTT_	 --
Microphone Multiplex System Provides Multiple Outlets from Single Source 
The problem: 
To use a single source of audio signal to provide 
multiple audio outputs that can be connected to many 
low impedance microphone inputs simultaneously. 
The solution: 
A microphone multiplex system that will accept a 
signal from a single source (a program mixer or any 600-
ohm line) and provide any number of low impedance 
outputs at microphone level with complete isolation 
between output channels. 
How it's done: 
The multiplexer consists of a single input trans-
former (600-ohm balanced or unbalanced bridge) 
for accepting any standard line input. The secondary 
of this transformer is connected to a master gain 
control and through isolation resistors to parallel 
cathode followers. The cathode followers give com-
plete isolation between channels and connect through 
individual gain controls to separate output trans-
formers. The levels of the master gain control and the
individual gain controls are adjusted so that the com-
bined loss will be approximately 55 db at each output. 
Approximately 65% of this loss is taken at the individ-
ual gain controls to keep the signal-to-noise ratio and 
distortion at an optimum. 
Notes: 
1. The multiplexer meets all broadcast standards. 
2. It has a response of 30 cps to 15 kc with less than 
1.0% distortion at —35 db output. 
3. Any input or output may be converted to high im-
pedance by elimination of the associated trans-
former. 
4. The input can be taken directly from a microphone 
with the addition of a preamplifier stage. 
5. Inquiries concerning this innovation may be di-
rected to:
Technology Utilization Officer 
Goddard Space Flight Center 
Greenbelt, Maryland 20771 
Reference: B66-10308
(continued overleaf) 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19660000307 2020-03-11T17:39:21+00:00Z
Patent status: 
No patent action is contemplated by NASA. 
Source: Raymond E. Lauver 
(GSFC-426) 
Brief 66-10308	 Category 01


Microphone multiplex system provides multiple outlets from single source

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server