Redesign circuit for different input voltage

Evening all, i've been digging around on the net to try and locate schematics to build a custom intercom system for a project i'm working on. There doesnt appear to be much avaliable in the market for what i'm looking to do but i've found a suitable "Party Line" intercom schematic that looks suitable, the circuit is currently designed for 4.5v - 9v input, yet as it's running on a boat, input voltage will be between 11 - 14.2v 

The schematic stimpulate that the voltage is regulated by R2,R3,C1

Would anyone be kind enough to offer any advice as to the correct components needed, and if possible an explanation so i can gain some understanding. The link below is to the schematic. 

Regards

Tom

 

http://www.edutek.ltd.uk/Projects/Proj_Stage_Intercom.html

If the LM386 is rated at 22V (some are, check the part number against the data sheet, they are generally rated for 15V, which is marginal on a 14V supply) and all the electrolytic capacitors have a high enough voltage rating, then it may run directly off a lead acid battery.
If the battery is on on a charging system off the engine, then you can get large voltage spikes which will take out ICs at the drop of a hat.
In that case it is customary to use automotive grade linear regulators, which tolerate large load dumps, reverse polarity, etc. If the battery is charged off solar cells, then this is not an issue.
The components R2, R3, C1 do not regulate the voltage, they bias the 741 amplifier up to half rail, since there is only a unipolar power supply.
If it won't run off 14V, the alternatives are to put some more diodes in series with D1, the regulation won't be brilliant, or use a resistor and zener diode, SMPS or linear regulator to drop you input voltage down to 9V.
Cheers,
Richard

Hi,

From the project you've shared, it provides quite a good circuit already and the components are stated in the circuit itself. Basically, intercom works like a basic walkie talkie but with much more features and uses standard lines like the telephone.

Now for the circuitry, it would be hard to discuss each part included there. it would be best if you had an idea with the components in the circuit itself. The R's are resistors, C's for capacitors, B for battery, IC for opamps, D for diodes.. But of course I would assume you know that ..

Now for your objective, what you'd want is a circuit that can work with different voltage level? Can you state your parameters?