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Help Please

  • Thread starter nntp.broadband.rogers.com
  • Start date
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nntp.broadband.rogers.com

Jan 1, 1970
0
I have a cordless phone which I am hoping to modify. It has no volume
control for the handset, and it is much too low volume. I was wondering
what I would have to do in order to be able to add a volume control or at
least increase the volume of the phone. I do have very basic electronics
skills, but I do need the help of the experts out there ;)

Please reply to the group.


Greatly appreciated.

Thank you.
Dave
 
D

default

Jan 1, 1970
0
I have a cordless phone which I am hoping to modify. It has no volume
control for the handset, and it is much too low volume. I was wondering
what I would have to do in order to be able to add a volume control or at
least increase the volume of the phone. I do have very basic electronics
skills, but I do need the help of the experts out there ;)

Please reply to the group.


Greatly appreciated.

Thank you.
Dave
Adding a control (a potentiometer) won't necessarily increase the
volume. The audio gain stage has to have the voltage and power gain
to increase the volume.

How you go about it would be dependant on a lot of conditions you
don't mention here.

Do you have a schematic? Do you know the impedance of the earpiece?

With a sufficiently high impedance earpiece a single transistor power
amp would probably work (at some sacrifice of battery life). Another
possibility might be to use one of the IC audio amps (LM386 if my
memory serves me), a power op amp, or op amp with external power
boosting transistors. More complicated, but the battery life would be
better.

Then there's the problem of shutting down the amp when you're not
using it (to conserve battery power). Is there a mechanical switch
that controls power when you use the phone? If not, you may need to
use an amplifier with built in sleep/mute function and would need a
way to (de)activate it.

There may already be enough gain there and it is just not used - the
gain may be set with a voltage divider (like a volume control - or it
may actually have a control in there somewhere). Gain may also be set
at an internal IC with a single external resistor.

The best options - hope there is some way to increase the output by a
tweak to the existing circuit, or find an earpiece transducer with
higher efficiency than the one in there and replace it.
 
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