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Telephone Ring Generator Using Switching Supply – Circuit Schematic
Telephone Ring Generator Using Switching Supply
The telephone ring generator shown below generates the needed high voltage from a simple switching mode power supply (SMPS) which employs a CMOS Schmitt Trigger...
TELETEXT devices – Circuit Schematic
TELETEXT devices
Test signals inserted in the lines of the vertical blanking interval, defined by the TV standard, e. g. for the 625 standard the CCIR together with the EBU issu...
TELETEXT devices – Circuit Schematic
TELETEXT devices
Test signals inserted in the lines of the vertical blanking interval, defined by the TV standard, e. g. for the 625 standard the CCIR together with the EBU issu...
PAL colour bar generator – Circuit Schematic
PAL colour bar generator
The first idea they was to work with 8.867238 MHz crystal (2 times the color carrier). When I read more about PAL video composite signal creation, I saw that, i...
PAL colour bar generator – Circuit Schematic
PAL colour bar generator
The first idea they was to work with 8.867238 MHz crystal (2 times the color carrier). When I read more about PAL video composite signal creation, I saw that, i...
FM Telephone Bug – Circuit Schematic
FM Telephone Bug
Here is a simple transmitter that when connected to a phone line, will transmit anything on that line (execpt the dial tone) to any FM radio. The frequency can ...
FM Telephone Bug – Circuit Schematic
FM Telephone Bug
Here is a simple transmitter that when connected to a phone line, will transmit anything on that line (execpt the dial tone) to any FM radio. The frequency can ...
Fax to Modem interface – Circuit Schematic
Fax to Modem interface
The circuit can be easily built to a small plastic box with telephone connectors in both ends. The circuit takes about 10-20 mA current, so if the circuit is no...
TAXI PHONE – Circuit Schematic
TAXI PHONE
This project is a dedicated device. It dials a single phone number when the handset is lifted. There are two different modes of operation.. A slide-switch on th...
DTMF Generation with a 3.58 MHz Crystal – Circuit Schematic
DTMF Generation with a 3.58 MHz Crystal
DTMF (Dual Tone Multiple Frequency) is associated with digital telephony, and provides two selected output frequencies (one high band, one low band) for a durat...
Chip recorder customizes phone ringer – Circuit Schematic
Chip recorder customizes phone ringer
Companies usually purchase one type of telephone for all employees, which is understandable, especially if they obtain a discount for buying in quantity. One ri...
TELEPHONE RING SIMULATOR CIRCUIT – Circuit Schematic
TELEPHONE RING SIMULATOR CIRCUIT
This project has been specially designed to introduce you to SMD (Surface Mount Devices). Surface Mount is really not new. It started as far back as 1940 with a...
Telephone Ring-Tone Generation – Circuit Schematic
Telephone Ring-Tone Generation
Here is a design that you can own, tailor to your specific needs, layout on your circuit board and put on your bill of materials. Finally, you will be in cont...