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HAMCOM (SSTV, RTTY, FAX...) modem using serial audio for TX - Ham Radio - Schematic - Modems and Soundcard interfaces __ Designed by Guy Roels ON6MU
HamComm Modem interface - I have recently done quite a lot of work on RTTY, using the HamComm program and been so impressed that I made a PCB to support the program. I think that I will continue to use the software, so I have registered it with the programs author: W. F. Schroeder, DL5YEC has obviosly put so much work into it. The program will send and receive RTTY up to 300 bauds as well as sending and receiving CW. I am very impressed with the programs ability to __ Designed by Harry Lythall-SM0VPO
Hands-Free Telephone - Transistor Q1 of the headset amplifier circuit amplifies the 30 mV signal, that would have gone to the earphones, to.5V, which sufficiently drives the stereo earphones. Capacitor C1 blocks any dc current from shorting back into the telephone base. Capacitor C2 provides the very important ac signal short around the amplifier__
Having secrecy in parallel telephones - Often a need arises for connection of two telephone instruments in parallel to one line. But it creates quite a few problems in their proper performance, such as overloading and overhearing of the conversation by an undesired person. in order to eliminate all such problems and get a clear reception, a simple scheme is presented here (Fig.1).__
High power Mobile phone Jammer - This project is the original High power mobile phone Jammer circuit, and all updates are posted here. All other versions are just copied from next.gr. First off all you should be very careful how to use this device. its fully illegal and so the purpose I post this Circuit is only for educational and testing reasons. This type of device is being used by security for ViPS, specially at their limousines to avoid bomb triggering while the car passes from the target cell phone-bomb__
Home Appliances Control using Telephone - Using this circuit, you can control up to seven electrical appliances through a telephone. The circuit can switch on/off the appliances in two modes. in the first mode, all seven or...__ Electronics Projects for You
Home Made PBX/PABX - I've been facsinated with telecommunications from an early age. When I was twelve or so I had an intercom system from which I could talk to most of the house from my corner of the kids' room. it was made out of the amplifier from a record player, and miscellaneous parts from old TV sets. When I was fourteen someone gave me a WW2 vintage shortwave receiver with a blown power supply. __ Designed by Markus Wandel
How to Build: Cell Phone Jammer - Cell phone jammer is an electronic device that blocks transmission of signals between a cell phone and a base station. By using the same frequency as a mobile handset, the cell phone...__ Electronics Projects for You
How to record telephone conversations - Sometimes it is useful to record telephone conversations. The easiest way is to go to a shop and buy a telephone conversation recording adapter which is connected between telephone line and the tape recorder. Those recording adapters are usually connected between telephone line and the telephone, but there are also other type available __ Designed by Tomi Engdahl
How to ring a telephone - People who read my telephone intercom article often ask what's so hard about ringing a telephone bell. The trouble is that you need AC at 20Hz and 40-90VRMS. That's not exactly the sort of AC that's easy to generate. if you do it at low voltage, you need a special transformer to transform it up -- a regular power transformer is no good at 20Hz -- and if you do it at high voltage, you need dangerous supply voltages and high-voltage components __ Designed by Markus Wandel
Incoming call indicator - it is a relatively simple circuit, with which we can have optical and sound clue, when we have telephone ring in the line of telephone. The calls in the line, are changed in pulses of frequency 400 HZ from the IC 2, in exit 3. Then via the IC 4, after they are strengthened at two times, they can be drive to the entry of amplifier and a loudspeaker, so that we hear the ring, in what level we want. The desirable level of sound __ Designed by Sam Electronic Circuits 8/01
Infinity Bug - This project requires a high degree of soldering. it uses surface-mount resistors, capacitors transistors and diodes. it can only be assembled on the PC board supplied (circuit 02/07) __ Contact Collin Mitchell
Intercom Preamp - A very convenient way of making an intercom is to use a loudspeaker as a microphone. This is a preamp with a low input impedance suitable for this purpose __ Designed by Richard Torrens
Intercom system - When I was 12 years old, I gained all the parts and skills I needed to make a 2-way intercom system. it consisted of a speaker at the near end, a speaker at the far end, an audio amplifier from a record player, an impedance matching transformer, and a 4PDT "push to talk" switch which reversed the roles of the two speakers __ Designed by Markus Wandel
Intercom using LM386 - Keep in touch with your family members from one room to another and also from outside areas such as the garage, using this intercom circuit for bidirectional communication. The advantage of...__ Electronics Projects for You
Intercom with fader - Suitable for tandem bicycles and motor cycles. Connects to iPod and similar MP3 audio players. __ Contact Flavio Dellepiane, fladello @ tin.it
Intercom with speaker as microphone - A very convenient way of making an intercom is to use a loudspeaker as a microphone. This is a preamp with a low input impedance suitable for this purpose __ Designed by Richard Torrens
Intercom-Headset-Microphone (Carbon)-Using Model 34 - No description, just schematic - OpAmps Lab inc is the manufactor ofAmplifiers (Video / Audio / Distribution / Microphone / Equalization / Line / VCA / Power) , Switchers (Routing / Assign / Matrix) , Mult (Press) (Network-Feed) Boxes, Audio Transformers, Oscillators, Power-Supplies, Custom Sub-Systems. __ Application OpAmps Lab Inc.
InterCommunication - This is a great intercom circuit that can be used in many ways. it uses 22V to operate and maybe it will work at a lower voltage (you can try it). For input/output it uses a loundspeaker (20-45 Ohm) on each side. __
Intercom-Party-line-Using Model 34 - No description, just schematic - OpAmps Lab inc is the manufactor ofAmplifiers (Video / Audio / Distribution / Microphone / Equalization / Line / VCA / Power) , Switchers (Routing / Assign / Matrix) , Mult (Press) (Network-Feed) Boxes, Audio Transformers, Oscillators, Power-Supplies, Custom Sub-Systems. __ Application OpAmps Lab Inc.
Isolated indicator signals telephone line's status - 06/08/06 EDN Design Ideas: Micropowered circuit shows off-hook phone Design by Yongping Xia, Navcom Technology, Torrance, CA
Isolated Telephone Interface - This circuit allows you to record audio from a telephone line into a tape recorder or computer soundcard. Most of the parts for this circuit can be scrounged from an old modem, with some work, it is possible to rewire the modem circuitry and use the old modem case __ Designed by G. Forrest Cook
KD2BD Pacsat Modem - The KD2BD Pacsat Modem is a low cost, high performance 1200 bps BPSK modem designed to interface between a packet radio terminal node controller (TNC) and an amateur satellite ground station, and allows full-duplex access to the 1200 baud "Pacsat" constellation of amateur satellites. __ Designed by John A. Magliacane, KD2BD |
