12-09-2017, 10:31 PM
I finally silenced all of the telemarketers, but that ain't what this here post is about.
Yesterday, I mentioned that I would be building a call progress tone generator today. As the name suggests, it's an electronic thingamabob that generates the dial tone, busy signal, ringing tone, and other audible signals to keep the caller informed about the progress of a call attempt. And here here it is:
https://imgur.com/a/t39y2
I had originally intended to build the whole module on a single board, but as I got to laying out the components, I became concerned that there wouldn't be enough room for all of the bias resistors, so I stuck part of it on a little headboard instead. That ended up saving my bacon because I made a mistake when building the headboard, and had to do it all over. If I'd done it as a single board, I would've had to redo the whole module.
So here's how this thing will (hopefully) work. The thing at bottom right is a microcontroller board that operates the module in response to commands sent over a USB connection from the main computer. The socket at bottom right is for the tone generator chip itself. The blue box above it is a relay. When the module is powered up, the tone chip's enable pin is connected through the relay to a power-on-reset circuit. After a few seconds, the microcontroller tells the relay to connect the enable pin to an output pin on the microcontroller. The socket on the headboard is for a channel selector chip. The microcontroller instructs that chip to route the tones from the tone generator to one of eight telephone lines.
Yesterday, I mentioned that I would be building a call progress tone generator today. As the name suggests, it's an electronic thingamabob that generates the dial tone, busy signal, ringing tone, and other audible signals to keep the caller informed about the progress of a call attempt. And here here it is:
https://imgur.com/a/t39y2
I had originally intended to build the whole module on a single board, but as I got to laying out the components, I became concerned that there wouldn't be enough room for all of the bias resistors, so I stuck part of it on a little headboard instead. That ended up saving my bacon because I made a mistake when building the headboard, and had to do it all over. If I'd done it as a single board, I would've had to redo the whole module.
So here's how this thing will (hopefully) work. The thing at bottom right is a microcontroller board that operates the module in response to commands sent over a USB connection from the main computer. The socket at bottom right is for the tone generator chip itself. The blue box above it is a relay. When the module is powered up, the tone chip's enable pin is connected through the relay to a power-on-reset circuit. After a few seconds, the microcontroller tells the relay to connect the enable pin to an output pin on the microcontroller. The socket on the headboard is for a channel selector chip. The microcontroller instructs that chip to route the tones from the tone generator to one of eight telephone lines.
