DAA circuit emulates central-office operation:  07/08/99 EDN Design Ideas  / (added 2/06)  [Note: File contains multiple circuits.  Scroll to find this one.]  The Mitel MH88422 data-access arrangement (DAA), a thick-film hybrid module, contains a complete interface between duplex voice- or data-transmission equipment and an analog telephone line. It provides transformerless, optoisolated two-to-four-wire conversion with transhybrid loss cancellation and operates from a 5V supply. The DAA also consumes low on-hook power. Figure 1a gives Mitel's typical application circuit. The Tip and Ring lines connect to a central-office or private-branch-exchange line, and the interface mimics the operation of a telephone set. The modification in Figure 1b changes the function of the interface such that an ordinary single-line telephone can connect directly to such systems as a voice/touch-tone peripheral device....

DC/DC Converter operates from Phone Line:  01/15/98 EDN-Design Ideas  /  (added 09/05)  DC/DC converters for use inside the telephone handset require operation from the high-source-impedance phone line. Additionally, the CCITT specifications call for maximum on-hook power consumption of 25 mA. The dc/dc converter in Figure 1 is 70%-efficient at an input power of 25 mA, providing 5V at 3.4 mA. Controlled, low-peak switch current ensures that the ­48V input line experiences no excessive voltage drops during switching.

Debugging IP Router Subsystems--Logic Analysis Tools for POS, Gigabit Ethernet and ATM:  Agilent Application Note   (app note added 6/06)

Designing High-Speed Digital Systems for Logic Analyzer Probing:  Agilent Application Note   (added 6/06)

Detecting a telephone RING :  ASCII format (circuit design added 10/06) jun 21, 2006

Differential Scope Probe Delivers 6GHz Bandwidth to the Screen:  02/20/03 EDN-Design Ideas / (added 8/03) With digital scopes that offer 6-GHz bandwidth suddenly almost commonplace and with industry participants now recognizing differential signaling as all but essential for sending multigigahertz signals across pc boards and backplanes, you shouldn't be surprised at the proliferation of ultrawideband, active, differential scope probes.

Digisound Ring Modulator:  (circuit / design added 8/03)

Digital PBX Linecard and Terminal:  National Semiconductor - Application Note   (app note added 6/06)

Digital/Standard Phone Line Tester :  ASCII format (circuit design added 10/06) jun 21, 2006

Digital/Standard Phone Line Tester:  make sure that the line is suitable for modem use and your PCMCIA does not damage if you plug it in (added 5/02)

DMOS Devices for Telecommunications:  Supertex Semiconductors  (app note added 2/06)

Doorphone Intercom:  (circuit / design added 8/03)

DSL Filter (phone-line):  (circuit added 9/04)

DSL Modem (CPE):  Intersil Application Block Diagram  (app note added 6/06)

DTMF Coder Makes Low Cost Sine Wave Generator:  10/13/94 EDN-Design Ideas / (added 3/03) A telephone DTMF IC produces, by design, two tones if you connect a single intersection of the IC's 4[x]4 keypad matrix (Fig 1). (Telephones commonly have 3×4 keypads but, unknown to many people, the applicable standard allows for a fourth row of four keys.) But, if you connect two key inputs at once, the IC produces a single-frequency, low-distortion sine wave. Table 1 lists values for an HM9187 (Winbond Electronics, Santa Clara, CA, (408) 943-6666. (DI #1592] ...  

DTMF Decoder for PC:  Displays DTMF digits on your computer screen in real-time.  (circuit added 8/06)

DTMF Generation with 3.58 MHz Crystal:  National Semiconductor - Application Note   (app note added 2/06)

DTMF Products for you:  DTMF decoder can be powered from a 9V battery or from your parallel printer, schematic and windows demo program, design by Schmidt Technologies (added 5/02)

DTMF Proximity Detector:  (electronic Circuit / Schematic added 10/04)

DTMF Receiver IC MT8870 Tester:  (electronic Circuit / Schematic added 10/04)

DTMF Tone Decoder:  hears touch tones and displays them as telephone numbers. (added 8/03)

Dual Tone Multiple Frequency DTMF:  National Semiconductor Application Notes first published04-Nov-1995 (app note added 5/02)

Ericsson phone to PC serial port interface:  (electronic circuit added 04/05)

Five band graphic equalizer:  This circuit uses a single chip, IC BA3812L for realizing a 5 band graphic equalizer for use in hi-fi audio systems.The BA3812L is a five-point graphic equalizer that has all the required functions integrated onto one IC. The IC is comprised of the five tone control circuits and input and output buffer amplifiers. The BA3812L features low distortion, low noise, and wide dynamic range, and is an ideal choice for Hi-Fi stereo applica-tions. It also has a wide operating voltage range (3.5V to 16V), which means that it can be adapted for use with most types of stereo equipment.
The five center frequencies are independently set using external capacitors, and as the…. (added 6/06)

FM Radio Telephone Bug:  (circuit / design added 8/03)

FM Telephone line Bug Transmitter:  (electronic circuit added 04/05)

Free Line Indicator Stops Interruptions:  12/07/00 EDN-Design Ideas / (added 11/05) / When only one phone line is available for two phones, each time you want to make a call, someone may be using the second phone. A simple circuit lights an LED, which indicates whether the line is free (Figure 1a). Batteries are unnecessary; the phone line powers the circuit, and an accumulator saves energy for an "in use" indication. A rectifier bridge ensures that the voltage is positive for the circuit. You can safely use this circuit on a private phone line, but you may need authorization before connecting it to your operator line....

Full-duplex doorphone with 3 Wires connection:  This circuit is a two-way (full-duplex) construction planned for use as door phone. To use, two pieces of the same circuit must be connected together with three wires: MINUS (ground), PLUS (power) and LINE. One of the circuits must be connected to a stabilized power supply, 6-30VDC.... (added 4/05)