Modem Circuits

Modem shutdown Indicator

The circuit has been designed to accommodate all those who dedicate many hours of their lives by exploring the endless pages of this site. Despite the fact that it consists of only three components (Most were not little!), Is able to provide an indication of whether it actually released the telephone line after a long connection via modem to the network. This can be particularly useful, since there In many cases, the computer claims that the telephone network connection has been interrupted, but the modem for some reason keeps the line engaged...

RS232 cable modem

First of all you have to build one cable adapter to connect the female 9pins connector of the modem, with female 9pins connector of the base of E-10G HPC. To build the null modem cable you will need: 2 male connectors with 9 pins. 15cm cable with 7 wires. The schematic at the left , its show how to connect the wires. When you finish it, you can connect the modem with E-10G. I have test it with: ISDN NetMod ( From Intracom, its used by the Greek organization of telecommunications, OTE ). U.S. Robotics 56K modem. For internet explorer try the iBrowser v1.17.02 or Pocket Browser v1.6. ..

Packet Radio with AVR

Here is some experimental hardware and software to transmit and receive AX.25 packets. It is essentially a PIC-E clone designed around a Atmel AT90S2313 with a few extra bells and whistles. I had picked up a couple of MXCOM MX-614s at the TAPR display (I also joined TAPR) at the Dayton Hamvention, and I needed a project to try them out on. I had designed many projects around Microchips PIC series micros, but had recently started experimenting with Atmel AVR micros. On the pic mail list this is referred to as 'going over to the dark side'. AVRs are PIC like risc processors, but with some additional features that made them slightly more suited for certain projects. AVRs are also very cost competitive against midrange PIC parts. ..

autodetects baud rate circuit MAX202 and PIC16C54

The popularity and easy access of RS-232 ports lend them to many communication projects. You can use a port as is” or as a tiny parallel port when the exchange uses only control lines. Before the asynchronous serial-data transfer between two devices can take place, you must ensure that both devices are configured to the same data format and transmission rate. Usually, the OS utility or application program on the host computer performs this task, which the OS or a combination of switches selects in the peripheral. ..

1. Because there is no DTR wire (modem pin 20) from Pilot. Pilot can simulate DTR line but this is not used at this moment (needs a pull-up) 2. This way we can not dial without a known dial tone if needed (like in some areas out of USA) 3. There no reason for this setting. Using X4 modem will dial as soon as it detects a known dial tone. Modem will not dial without a known dial tone (no good outside USA)...

The modem-access adapter (MAA) in Figure 1 has features that reduce problems when modems and phones share the same line. The design also overcomes the shortcomings of modem interference protectors. The design eliminates mutual interference between phones and modems, is compatible with the line-usage indicators on multiline phones, can search for an idle phone line in multiline installations, draws minimum power, and requires no changes to a PC modem`s hardware or software...

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...

The red boxes and symbols below represent functions provided by Intersil. Please click them for part numbers and links to parametric tables. Click on the Print Friendly link to view an expanded view of the application...

The 2400-bps modem in Figure 1 makes it easy to connect a Basic Stamp (Parallax Inc, www.parallaxinc.com) to a telephone modem. Using this circuit, you can call home via your PC and find out if the house is still there. The Basic Stamp2, BS2-IC, has the necessary programming space, and a 64-kbyte StampMEM memory-storage board enhances site data collection...

A simple modem provides an inexpensive way to link your IBM PC or compatible computer with a remote system. The modem, which transmits data asynchronously at 300 baud, is easy to build and features both autodial and autoanswer...

This application note describes the V.34 Modem Interface and the benefits obtained when the DS8933 and DS8934 Line Drivers and Receivers are employed. The following sections are covered. # V.34 Standard # DS8934 and DS8933 # Async Application # Sync Application # Driver Characteristics # Receiver Characteristics # RS-232 and RS-423 # Summary # References..

No description available...

The LT1886 is a high speed dual power amplifier with excellent high frequency distortion performance. The LT1886 features a 700MHz gain-bandwidth product, 200V/ms slew rate and over 200mA of output current drive in a small SO-8 package. Using only a single 12V supply, the LT1886 is the best choice for the line driver in ADSL CPE modems (customer premises equipment)...

This is a prototype of the WA4DSY 56KB RF modem. It is intended for use on amateur packet radio networks. The modem generates RF in the 28 to 30 mhz range and requires and linear transverter to convert the signal to a UHF or microwave ham band. The digital interface is synchronous serial. The modem supplies TX and RX clocks. For more details see the various links below...