Multiple radios, one speaker?

what? if I dont misunderstand your meaning.

are you going to use one speaker to listen more than two radio station at one time? or listen two phone input?

do you think they will be interference each other? and you can listen nothing.

Look at mixers in the music industry. A sound card in a PC can do it for you.

I saw a mixer kit at the electronic hobby store.

What is your intended application?

if you want a two or more channel change into one channel, you can use mixer, if not, only two redio into one, you will hear interference.

the mixer is not a difficult engineering. active cuicirt or transformer can all do . high resistance input is convinient to finish the mixdown.

issue is which level will you get from?

I I remember that being done back when I was working for a sound contractor.

The separate inputs were applied to the primaries and the secondaries were connected in series and connected to a speaker or another audio input. This was the early version of mixers before fully electronic versions came out (using integrated circuits).

This is fine for mixing microphones and other audio inputs but I would not use it to listen to two or more radio stations. Much too confusing!

It's used for Police vehicles with multiple radios. It was said that it was no different than having two seperate speakers going at the same time as done with one speaker for the two radios. It was setup to reduce clutter in the vehicle.

Is this intended for Police vehicles? or are you working on a personal project and want a similar device?

Try www.mfjenterprises.com This is the sort of thing that us ham radio folks like to do and MFJ makes all kinds of ham radio accessories, they just might have what you want.

Aircraft have a device that dose exactly this. With aircraft it is not uncommon to have multiple radios tuned to separate frequencies all driving the single speaker or headphones. They also have inputs for microphones that enable more than on pilot to either talk to the others or drive one of the transmitters.

If you live in the USA have a look at some of the aircraft disposal places as you may be able to pick up a second hand one to do what you want off the shelf.

************* Quote *************Aircraft have a device that dose exactly this. With aircraft it is not uncommon to have multiple radios tuned to separate frequencies all driving the single speaker or headphones. They also have inputs for microphones that enable more than on pilot to either talk to the others or drive one of the transmitters.************* Quote Ends *************Further to your comments:Aircrafts, Ships & Boats, Army Tanks and various other communication equipments like mobile communication Setups have more than one Wire-less sets in combination Set Inter-com [IC] has more than one control-units for each crew-member. All wire-less sets are connected through IC to control-units. Priorities for sound-Over-ride is set in IC set, that means that most important will Over-ride the sound. eg In Army tanks there are 2 Wireless sets; Main connected to Headquarters, Aux connected to Squarden-Members And IC to Tank's Crew-members. Commander will take-over if signal from HQ over-ride or to Aux set if Squadron-Commander comes on Aux set.Normally all crew-members remain on IC and switch to Main or aux when required.

Almost same system is in aircrafts. Main for communication to Civil Aviation Controller, Guard-channel for SOS Signals, IC for Cabin-crew.

In IC an audio-mixer [w/o transformer it was Electronic-Tubes' time] was used as in OPs Amplifier is used now

Why transformers?

See figure 9

http://colomar.com/Shavano/intro_opamp.html