Hi All,
I was just wondering whether any of you electronics whizzes could possibly help me with a little project I'm working on...?
I'm trying to construct a four station push-to-talk intercom for use in a theatre. It needs to be cheap so I'll try to use standard PC headsets with two 3.5mm jacks. I imagine it'll be constructed (roughly) as follows:
There will be a central base station - the only directly powered component. This will contain a 12V power supply and the majority of the electronics required to make the base stations work. It'll have four amplifiers such as the LM386 to provide reasonable volume for the headsets. Each headphone amplifier will use a circuit like those on page 5 of the amplifier data-sheet.
Each remote station will have sockets for headphones and microphones. They need a volume control for the headphones and a mute button for the microphone (a simple toggle switch that cuts off the microphone would do nicely...) They will have also have an 'Alert' LED to for when people aren't wearing their headsets.
To keep costs down, I'd like to connect each remote unit to the base station with standard 4-core RJ11. This will use one core for ground, one for microphone, one for headphone and one for alerting.
The main thing that's confusing me is how to combine the microphone inputs. I need all four people to be able to talk simultaneously (in theory) and I'm fairly sure that it's not just possible to put the microphones in parallel (though correct me if I'm wrong!) because it would knacker the impedances.
Other than four amplification circuits, what do I need. In fact, do I even need four amplification circuits or can I connect four headsets in parallel to one larger amplifier if they all need to hear the same thing?
Any advice, web links (I've done much googling!) or thoughts greatly appreciated!
I was just wondering whether any of you electronics whizzes could possibly help me with a little project I'm working on...?
I'm trying to construct a four station push-to-talk intercom for use in a theatre. It needs to be cheap so I'll try to use standard PC headsets with two 3.5mm jacks. I imagine it'll be constructed (roughly) as follows:
There will be a central base station - the only directly powered component. This will contain a 12V power supply and the majority of the electronics required to make the base stations work. It'll have four amplifiers such as the LM386 to provide reasonable volume for the headsets. Each headphone amplifier will use a circuit like those on page 5 of the amplifier data-sheet.
Each remote station will have sockets for headphones and microphones. They need a volume control for the headphones and a mute button for the microphone (a simple toggle switch that cuts off the microphone would do nicely...) They will have also have an 'Alert' LED to for when people aren't wearing their headsets.
To keep costs down, I'd like to connect each remote unit to the base station with standard 4-core RJ11. This will use one core for ground, one for microphone, one for headphone and one for alerting.
The main thing that's confusing me is how to combine the microphone inputs. I need all four people to be able to talk simultaneously (in theory) and I'm fairly sure that it's not just possible to put the microphones in parallel (though correct me if I'm wrong!) because it would knacker the impedances.
Other than four amplification circuits, what do I need. In fact, do I even need four amplification circuits or can I connect four headsets in parallel to one larger amplifier if they all need to hear the same thing?
Any advice, web links (I've done much googling!) or thoughts greatly appreciated!