Off Hook Phone Line Supplies 150 MW:  09/01/94 EDN-Design Ideas / (added 3/03) For systems that require 150 mW or less, the power supply in Fig 1 draws power from ordinary phone jacks without interrupting the voice signal, thereby eliminating the need for batteries and ac adapters. Built into peripheral equipment such as PCMCIA modem cards, this circuit can spare the battery in a host computer. The circuit is useful in portable systems that connect to subscriber (household) telephone lines, such as modems and telephone test sets....    

Off line Telephone tester #2:  (electronic circuit added 10/05)

Off Line Telephone Tester:  Here is a circuit of an off-line Telephone tester which does not require any Telephone line for testing a Telephone instrument. The circuit is so simple that it can be easily assembled even by a novice having very little knowledge of electronics. FAIR WARNING -- THIS SITE HAS ANNOYING POP UP ADS. (added 5/02)

Old Phones as an Intercom:  (circuit added 7/02)

Optimized DCE Interface for V.34 Modems using the DS8933 and DS8934 Line Drivers and Receivers:  National Semiconductor - Application Note   (app note added 2/06)

Parallel Telephone with Secrecy and Call Prevention:  (electronic Circuit / Schematic added 10/04)

Parallel Telephones with Secrecy #2:  This system will enable the incoming ring to be heard at both the ends. The DPDT switch, installed with each of the parallel telephones, connects you to the line in one position of the switch and disconnects you in the other position of the switch. At any one Time, only one telephone is connected to the line. To receive a call at an end where the instrument is not connected to the line, you just have to flip the toggle switch at your end to receive the call, and act as usual to have a conversation. As soon as the position of the toggle switch is changed, the line gets transferred to the other telephone instrument. (added 3/03)

Parallel Telephones with Secrecy:  (electronic Circuit / Schematic added 10/04)

PCS: not just another cell phone:  11/21/96 EDN-Design Feature / (added 11/05)  Building Thanks to the availability of low-cost digital chip sets, PCS is now becoming affordable and finding use in fax, e-mail, and palmtop computer functions. Capitalizing on that affordability, PCS providers and IC makers are hoping to lure consumers with imaginative and user friendly features: large, easy-to-read displays; ergonomic touchscreens; and speech recognition.—Stephen Kempainen, Technical Editor

Phone Broadcaster #2:  (electronic Circuit / Schematic added 10/04)

Phone Broadcaster:  (electronic circuit added 10/05)

Phone Busy Indicator:  simple busy indicator, does not meet regulations of many countries because this circuit draws excessive continuous current from the ph1-line even when not active and this can cause problems with Telephone system (added 5/02)

Phone Hold with Music:  (electronic (schematic / circuit added 4/02)

Phone in Indicator:  (electronic (schematic / circuit added 4/02)

Phone in Use indicator:  (circuit / design added 8/03)

Phone in Use Light:  (circuit / design added 8/03)

Phone in use:  (circuit / design added 8/03)

Phone in-use :  ASCII format (circuit design added 10/06) jun 21, 2006

Phone In-Use Light - (manual) :  ASCII format (circuit design added 10/06) jun 21, 2006

Phone Line to Audio :  ASCII format (circuit design added 10/06) jun 21, 2006

Phone Line to Audio:  (circuit / design added 8/03)

Phone line Voltage monitor meets FCC specs:  08/19/04 EDN Design Ideas  /  (added 1/05)  When you design equipment that interfaces to a phone line, it is often desirable to be able to monitor the dc voltage on the line. This ability can be useful, for example, to determine whether a line is in use before attempting to go off-hook and possibly interrupting somebody's phone call. FCC regulations place strict limits on the amount of leakage current an on-hook device can draw from a ph......

Phone Off Hook Indicator:  (circuit / design added 8/03)

Phone Off-Hook Indicator :  ASCII format (circuit design added 10/06) jun 21, 2006

'phone rang' indicator light :  ASCII format (circuit design added 10/06) jun 21, 2006

Phone Rang Indicator Light:  (circuit / design added 8/03)

Phone ring circuit schematic:  (electronic circuit added 04/05)

Phone Tap #1:  will record any conversation on any ph1-on same line, the circuit seems to be a bad design because it does not provide proper isolation and has too low DC impedance (can keep you line off-hook all the Time) (added 5/02)

Phone to audio interface (SSI202 input) :  ASCII format (circuit design added 11/06) jun 21, 2006

Phone to Audio Interface:  (circuit / design added 8/03)

Phone Wire RJ 11 jacks and optocouplers Build a Bus:  12/24/04 EDN Design Ideas  /  (added 1/05)  Although cutting-edge technology reaps publicity, the real world often runs on modest hardware that's just "good enough" for home automation, alarm systems, and equipment-monitoring application

Phone-In-Use indicator :  (electronic Circuit / Schematic added 10/04)

Phone-In-Use indicator :  ASCII format (circuit design added 10/06) jun 21, 2006

Phono PreAmplifier:  Simple circuitry suitable for moving-magnet cartridges Passive high-frequency equalization  (added 3/05)

Playing a Mac through a Standard Telephone Line:  how to get sound from computer to Telephone line (added 5/02)

POS-PHY Level 4 SystemIO Cores by Xilinx (Speaker Notes):  Agilent Application Note   (app note added 6/06)

POS-PHY Level 4 SystemIO Cores by Xilinx:  Agilent Application Note   (app note added 6/06)

Programmable Central Office and Private Branch Exchange Linecards:  National Semiconductor - Application Note   (app note added 2/06)

Radio Remote Control using DTMF #2:  Here is a circuit of a remote control unit which makes use of the radio frequency signals to control various electrical appliances. This remote control unit has 4 channels which can be easily extended to 12. This circuit differs from similar circuits in view of its simplicity and a totally different concept of generating the control signals. Usually remote control circuits make use of infrared light to transmit control signals. Their use is thus limited to a very confined area and line-of-sight. However, this circuit makes use of radio frequency to transmit the control signals and hence it can be used for control from almost anywhere in the house. Here we make use of DTMF (dual-tone multi frequency) signals (used in telephones to dial the digits) as the control codes. The DTMF tones are used for frequency modulation of the carrier. At the receiver unit, these frequency modulated signals are intercepted to obtain DTMF tones at the speaker terminals.... (added 09/05)

Radio Remote Control using DTMF:  (electronic circuit added 10/05)

Remote control using telephone #2:  (electronic circuit added 10/05)

Remote Control using Telephone:  Here is a tele-remote circuit which enables switching "on" and "off" of appliances through Telephone lines. The circuit described here can be used to switch up to nine appliances (corresponding to the digits1 through 9 of DTMF the Telephone key-pad). The Telephone can be used to switch on or switch off the appliances also while being used for normal conversation. FAIR WARNING -- THIS SITE HAS ANNOYING POP UP ADS. (added 4/02)

Ringing Phone Light Flasher:  when the ph1-rings, lights connected to circuit flash (added 3/03)

Rotary Dial Phone:  (schematic added 10/06)

SB-100: Subscriber Line Card for Central Office Telephone Switching Equipment:  National Semiconductor - Application Note   (app note added 2/06)

SB-101: Digital PBX Linecard and Terminal:  National Semiconductor - Application Note   (app note added 6/06)

SB-105: Programmable Central Office and Private Branch Exchange Linecards:  National Semiconductor - Application Note   (app note added 2/06)

Shielding and Guarding:  AN-347 - Analog Devices Application Notes  (app note added 6/06)How to Exclude Interference-Type Noise. What to do and Why to do it-A Rational Approach

Silent Telephone Alert:  (electronic (schematic / circuit added 4/02)

Silicon MW Broadband Amplifier MMIC's (7/20/88) :  Application Note - California Eastern Laboratories - Doc #918  (app note added 6/06)

Simple Circuit to Connect telephone Equipment to Audio Mixer:  I have used this type of circuits for quick testing of telephone equipment. This is a quick hack that does not exactly resemble the characteristics of the real telephone network, but is enough for this kind if applications. If you want better simulation, change the resistor to 600 ohm and increase the power supply voltage. And by the way you can also feed signals to telephone if you connect the circuit output wires to small amplifier output. (added 11/05)

Simple Circuitry for Cellular Telephone/Camera Flash Illumination:  AN95 - Linear Technology - This publication concerns implementation of high quality "Flash" illumination in cellular telephones/cameras. Performance vs LED based illumination is discussed and flashlamp operation reviewed. Considerations for support circuitry are given, and a practical circuit, accompanied by performance data, is described. Layout and RFI issues are treated and a sample layout provided. An appended section details operation of the LT3468 flash capacitor charger used in the text's circuit and lists appropriate magnetic components.

Simple Phone Tap #1:  will record any conversation on any ph1-on same line, the circuit seems to be a bad design because it does not provide proper isolation and has too low DC impedance (can keep you line off-hook all the Time) (added 5/02)

Simple Telephone Recorder:  This recorder can be connected to the telephone lines just about any place, and no external power source is needed. The tape recorders switch terminals are applied to a pair of transistors, connected as Darlingtons, that are used to turn the recorder on and off. When the telephone is off-hook theres usually about50 VDC across the phone that's divided over R1, R2, and R4, so that Q1s base is negative enough to keep the recorder off. Pick up the receiver, and the voltage drops to5 V. That leaves not quite-enough voltage on Q1s base to keep that transistor at cutoff, so the recorder begins. Remember to keep your recorders switch in the on position, and depending on how many people use the telephone, remember to rewind or change tapes occasionally! (added 3/03)

Simple Telephone Ring Tone Generator:  (electronic Circuit / Schematic added 10/04)

Simulate signals for telecomm tests :  09/11/98 EDN-Design Ideas  / (added 2/06)

Single cell flashes white LED:  12/11/03 EDN Design Ideas  / (added 2/06)   Many portable appliances and other products that must operate from a single cell are restricted to working at very low voltages. It is thus difficult to drive white LEDs that typically have a forward voltage of 3 to 5V. The ability to flash the LED with a supply voltage as low as 1V presents additional complications.

Single Chip Modem Provides Low-Cost Data Communication:  National Semiconductor - Application Note   (app note added 2/06)

Smart Phone light:  (electronic circuit added 10/05)

Smart Phone:  Intersil Application Block Diagram  (app note added 6/06)

Smart Ringing Phone Light:  The circuit shown here is used to switch on a lamp when the Telephone rings, if the ambient light is insufficient. FAIR WARNING -- THIS SITE HAS ANNOYING POP UP ADS. (added 5/02)

Soft on/Off Switch:  Modern electronic equipment incorporate "push-to-on-push-to-off" switches that do not make the clicking noise as with old equipment. An example of this is the power button on a ATX computer cabinet. Here is a circuit that does the same. It can be used to turn on/off any electronic/electrical equipment that operates on any range of voltages. FAIR WARNING -- THIS SITE HAS ANNOYING POP UP ADS. (added 5/02)

Subscriber Line Card for Central Office Telephone Switching Equipment:  National Semiconductor - Application Note   (app note added 2/06)

Switched capacitor IC and reference form elegant48 to +10V converter:  04/24/03  EDN-Design Ideas / (schematic / circuit added 11/03) A system designer must almost always face a trade-off in choosing the right part for an application. The trade-off usually involves performance, price, and function. An example is the issue of powering circuits from a telecom-voltage source. Telecom systems almost exclusively use high-potential negative rails, such as 48V...