This toy intercom system is way better than a pair of tin cans and some string

toy-intercom-system

On his blog, [Kenneth Finnegan] recently showed off a replica of a fun toy he used to play with as a kid, a telephone intercom system. The setup is pretty simple, requiring little more than a pair of analog phones, a battery, and a resistor.

The phones are connected to one another using a standard telephone cable, but [Kenneth] uses … Read the rest

Detecting DTMF tones from scratch

If you’ve ever wondered about the best way to detect dial and DTMF tones from a phone line, [Debraj] is your man.

[Debraj] built a DTMF detector using the Goertzel algorithm. Normally, when we think about detecting tones, we pull FFT out of our bag of tricks. The Goertzel algorithm isn’t as computationally complex as FFT and can be … Read the rest

Ever wonder where cool interactive museum exhibits come from?

[Victor's] girlfriend works at a museum and enlisted his expertise in designing an interactive detective game for kids visiting the museum. The vision was for the kids to discover phone numbers that they could call for clues. Originally he planned to display the clues on a character LCD, but obviously it’s much neater to hear the clues in the … Read the rest

Simple DTMF decoder pulls numbers from YouTube videos

dtmf_decoder

While many of us have banished land line telephones from our houses, there are still quite a few people who utilize POTS lines today. These analog phone systems use Dual Tone Multi Frequency (DTMF) signals in order to audibly represent all of the keys on a telephone keypad and place calls. [Brad] over at LucidScience decided that it would be … Read the rest

Free home phone method uses parts we’re familiar with

[Headsheez] found a way to get his home phone service for free. He’s using a set of tools that we’re familiar with to route service from a typical analog phone system (which involves the extensions wired into your home) through a server to the Internet. On the hardware side of things this starts out with an Analog Telephone Adapter … Read the rest

Remote operated security gate lets you phone it in

ring_detection_circuit

[Itay] has a friend who works in a rented office where the parking lot is secured by a remote-controlled gate. Unfortunately, while his friend shares an office with several people, they only received a single remote. To help his friends out, he built a small device that triggers the remote control whenever a phone call is received.

The remote modification … Read the rest

Paging system for your TV remote

[Matt] brought together a TV remote and cordless phone to add a locator system to the remote control. One of the best features of a cordless phone is the pager button on the base. When you press it the handset beeps until found. Matt gutted one and got rid of the unnecessary parts. He then cracked open his TV … Read the rest