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Music On Hold Box Circuit – Circuit Schematic
Music On Hold Box Circuit
Ul, an LS3404 melody chip is activated when hold SI is pressed, which causes SCR1 to conduct and hold the telephone line via Tl, Rl, and LED1. The voltage acro...
Phone Line Interface Circuit – Circuit Schematic
Phone Line Interface Circuit
This circuit should be useful for interfacing phone projects to the telephone line. ...
Telephone Ring Indicator Circuit – Circuit Schematic
Telephone Ring Indicator Circuit
A neon lamp can easily be added to the phone line to act as a ring indicator....
Telephone Bell Simulator Circuit – Circuit Schematic
Telephone Bell Simulator Circuit
This circuit is intended for use in a small private telephone installation. The ringing tone sequence is 400 ms on, 200 ms off, 400 ms on, 2 ms off. In the acc...
Telephone Ring Converter Circuit – Circuit Schematic
Telephone Ring Converter Circuit
The circuit is based on the TCM1506 ring detector/driver integrated circuit. It is a monolithic IC specifically designed to replace-the telephone`s mechanical ...
Music On Hold Circuit – Circuit Schematic
Music On Hold Circuit
When an asterisk * is pressed on the touch-tone phone, TCI a DTMF decoder, controls on-hold logic. Audio from the FM receiver IC4 is.placed on the telephone li...
Telephone Call Recording Circuit Circuit – Circuit Schematic
Telephone Call Recording Circuit Circuit
The dc voltage present on a telephone line is usually around 45 to 50 V on-hook and 6 V off-hook. This circuit uses This drop in voltage to activate a relay. T...
Modem/Fax Protector For Two Computers Circuit – Circuit Schematic
Modem/Fax Protector For Two Computers Circuit
This modem/fax protector can be used in telephone-line connections between a PC or a terminal and a distant computer. In this circuit, the SVPs (surge voltage ...
Telecom Converter Circuit – Circuit Schematic
Telecom Converter Circuit
The circuit supplies 1 A at +5 V from the -48-V supply commonly used in telephone equipment....
S Meter For Communications Receivers Circuit – Circuit Schematic
S Meter For Communications Receivers Circuit
Because many amateur receivers are fitted with an S meter that functions far from logarithmically, the proposed circuit should be a welcome extension of such r...
Telephone Intercom Circuit – Circuit Schematic
Telephone Intercom Circuit
An intercom using dual-modular wall jacks is shown in this circuit. If the wires are available in the home telephone cable,...
Very Simple Telephone Intercom Circuit Circuit – Circuit Schematic
Very Simple Telephone Intercom Circuit Circuit
Two telephones can be used as an intercom by using this circuit. Older style rotary phones that are nonelectronic might work best in this application....
Fax Mate Circuit – Circuit Schematic
Fax Mate Circuit
The fax mate separates the fax machine from the phorie line, rings the fax machine on command, connects equipment to incoming lines, and senses the end of the ...
Color-Bar Generator – Circuit Schematic
Color-Bar Generator
IC5 generates RS-170 NTSC synch. IC1, IC2, and IC3 make up the red, green, and blue video signals that drive the video ...
Tv Line Pulse Extractor – Circuit Schematic
Tv Line Pulse Extractor
This circuit uses a sync-generator chip, a counter, and a decoder to detect the horizontal sync pulse that occurs a...
Simple Ring Detector – Circuit Schematic
Simple Ring Detector
This circuit detects the 20-Hz approximately 86-Vrms ring signal on telephone lines and initiates action in an electri...
Telephone Message Taker – Circuit Schematic
Telephone Message Taker
This circuit operates on the ringing voltage of the telephone to trigger a tape recorder to record messages. Kl can...
Telephone Visual Ring Indicator – Circuit Schematic
Telephone Visual Ring Indicator
In this circuit, the ringing voltage on a telephone line causes NE-1 to break over, triggering SCR1, which ...
Extension Phone Ringer – Circuit Schematic
Extension Phone Ringer
The ac ringing voltage (typically 40 to 90 V at 26 Hz) is rectified by U1, the tone-ringer IC, and is used to drive ...
Phone-In-Use Indicator – Circuit Schematic
Phone-In-Use Indicator
The circuit receives its power from a 15-V wall adapter (not shown). The circuit takes advantage of the fact that th...