Hot answers tagged

11

None of the smartphones today have dedicated GPS chips in them, they only have a GPS capability that stems from byproduct features of the modem chips. That's not true. GPS functionality in phones is done either with a dedicated chip, or with a dedicated GPS receiver within a System-On-Chip (which is effectively the same as having a dedicated chip). ...


7

Notice the designators are C14A, C14B, C14C, etc. This likely indicates these capacitors are all part of a single capacitor array component. If the array the designer selected has too many individual capacitors than are actually needed, then shorting the unused ones avoids the possibility of static charge building up on them. If you look at the physical ...


6

Yes, you can use a delay and ignore the response, but if it is a response to sending the actual SMS itself, then that could take some time. You would have to send several SMS messages by hand to judge how long it might take the OK to come back, and then add on some margin to the longest delay seen. It would be much better to actually look for the OK ...


6

Yes, IPEX is a line/type of connectors made by LTI (LightHorse Technologies Inc). As @Passerby pointed out, IPEX mhf connector is the equivalent of Hiroshi U.fl (according to this website they are 100% compatible: http://www.wellshow.com/rf-connectors/mini-connector/ipex-mhf-connector/)


6

The problem is quite likely related to your breadboard. They are not very good for high currents. Why? Well there are a few reasons, but it all comes down to your components not being that well connected. Firstly you inevitably have a bunch of thin wires going between everything. I highly doubt your average jumper wire is rated for 2A. But even if it is, ...


5

Switching regulator design is complicated indeed, and it even requires a proper PCB layout thanks to the high frequencies and EMI involved. But it's by no means impossible when building it around a controller IC and following its datasheet's recommendations. But consider that for about the same 3 euros, you could buy a ready-made switching regulator module ...


5

You won't be able to get a v.92 link with both sides of the connection being analog. I'm a little rusty, but I was the technical lead for a large (10k+ subscriber) dialup ISP in the late 90s - early 00s. I think the maximum speed you'll be able to achieve with both ends being analog is 33.6k. Wikipedia seems to agree with me on this: http://en.wikipedia.org/...


5

The other answers seem to involve using 3.5 mm jacks and an audio cable just to carry a typical serial digital signal from the Raspberry Pi GPIO ports: e.g. wiring asynchronous serial, SPI or I2C to a dedicated external 3.5 mm jack which is not the audio jack on the Pi. I interpreted the question more along the lines "can I transmit digital data to a ...


5

Short answer: It's a brand thing. Long answer: All refer to micro RF coaxial connectors for 0-6Ghz applications based on the Hirose U.FL-series design. U.FL = U.FL series from Hirose Electric Group Specs: hirose.com/product/en/products/U.FL/ IPEX = MHF series from I-PEX Connectors Specs: i-pex.com/Products/Micro-RF-Coax-Connector Ya got me on IPAX... ...


5

The fears are unfounded - both technologies are fundamentally safe. The only conceivable damage from radio waves is heating of biological tissue and and Specific Absorption Rate (SAR) testing is specifically designed to ensure no harmful exposure levels to humans in nearby usage and Maximum Permissible Exposure (MPE) at distances past 20cm. "In the United ...


4

Here's a V92 modem module we use in one of our products. It takes RS232 style inputs (at 3.3V). While not a single chip, it is a single module. My only complaint is that it's not surface-mount.


4

You could probably use RS-485 for the task if you don't want to use this modems. It would help to post more information about what exactly this modems are. RS485 can help you as you could convert TTL signals into a twisted pair driven by a RS485 transceiver, as it works up to 4000ft. I could not request more information before making up an answer because I ...


4

I agree with Rennex answer and I want to add something. Using LM317 or other linear regulator in your case is very bad idea. You will loose a lot of precious battery energy on linear regulator. At 200mA ("normal operation"), with dropping from 24V to 5V regulator will waste: P = I * U = 0.2A * (24V-5V) = 3.8W


4

In order for SMS messages to be recieved, there absolutely, definitely has to be power going to the wireless modem. There is absolutely no way around this. Best thing you can do is to switch the modem on for a short period, say 15 seconds, which should be enough to receive any messages - do this say once every 5 minutes, or once an hour, or whatever. All ...


4

I used to manufacture a telecom device with a serial port. While it looks similar to an RJ-14 phone jack it is not. And RJ-14 connector has two rows of two pins with an offset. See red circle. The bigger holes are the connector's mounting holes. Some times serial ports use RJ-14 but with 6 conductors. If you look carefully at the gold contacts of the ...


3

I think you are possibly confusing two different issues. Throughout I'll be quoting from this page, which is superb and worth a read. Firstly we see this: The whole available frequency band is split into a distinct number of sub-channels. So we split our entire available frequency up, the page also says that sub-channels may be referred to as "carriers,...


3

I'd contact ntp.org. They have a pool of public NTP servers with DNS anycast for geographic proximity and are generally able to give good suggestions. You might be asked to use a subdomain (e.g. Debian uses "debian.pool.ntp.org") so if a malfunction in your devices causes a traffic storm this can be reflected without affecting the rest of the pool.


3

I assume that you are trying to connect your equipment to a uninterruptible power supply (UPS) of some kind. For your purposes, real power (watts) is given by P [watts] = V [volts] × I [amps] ÷ efficiency [%]. You may take the efficiency of the average wall power adapter to be 90%. (The other 10% is wasted as heat.) As AndrejaKo mentions, you then ...


3

After extending the initialization string of the GSM modem with 'AT+CSNS=4' the device was able to connect with analog modems.


3

In addition to what @goblinbox commented, another possibility to consider, would be to build a soft-modem yourself. A modern ARM processor should have enough chops to handle most of the signal processing stuff in software. According to the ARM guide, the only extra hardware needed is a 14-16bit linear CODEC at 8kHz and the PSTN interface circuit. The guide ...


3

It could work, but there would be some major disadvantages to the approach: Achieving a sufficient signal-to-noise ratio (SNR) will be very difficult, as you likely cannot control sources of noise. You'll probably need high-power directional transducers to achieve a strong enough signal to drown out the noise. Sorry for the pun. A commercial off-the-shelf ...


3

For distances up to as much as 10K feet you can consider the use of a differential signal pair that has drivers run off a 5V power supply. There are chips specially designed for this application. If your communication needs to be bi-directional then look into RS485 transceiver chips from companies such as TI, Linear Tech or Maxim. That would take a pair of ...


3

The nrf24l01+ is an IC. The FCC does not certify IC's. If you search around, you can probably find an FCC approve module that uses that particular IC. For small quantities, this may be a very cost effective way to go until FCC certification is in your budget.


3

A modem, in general terms, has three parts. The first is modem part, changing one signal to another, like dialup modulating and demodulating analog signals, a cable modem demodulating rf frequency or a fios modem changing fiber optic signals into a locally usable form. The second is a router, and the third an Ethernet switch (even if single port). When a ...


3

DTMF tones are only required for dialing out through an exchange. When connecting directly from modem to modem you are already connected, so the phone number is redundant! However the Dreamcast modem may expect to get various tones and voltages during the call (eg. dial tone, line voltage) while the receiving modem won't normally answer unless it gets ...


3

This evidences how each one of us sees the internet from his point of view. Starting by some basics have a look at this picture: Image Attribution : Chunte7 [CC BY-SA 3.0 (full license)] As you can see the internet can be divided into 4 layers, some times 5 by dividing the network access layer into other two layers, that are in the image on the right. ...


2

TCP/IP is not, strictly speaking, an OSI network - the OSI model only maps exactly onto the OSI network protocols (X25, X400 etc). There's also an iceberg hidden in your question of which the data card is just the tip: the 3G data network the card connects to ("UTRAN") is not a simple thing and includes several sorts of link. It's almost entirely ...


2

I figured it out. The modem had hardware flow control enabled by default. So I had to put it into null modem state. Its just a matter of shorting CTS and RTS lines each other. Now its working perfectly fine.


2

I used some generic modules, so here are some values to work with: voice call: 250 - 300 mA (unactive unused bursts: 20 - 50 mA) GPRS (2Tx, 3Rx slots): 340 - 410 mA This assumes having a matched antenna. The current consumption itself depends on the transmitted power and is thus dependend on the network. If you have a highly unmatched antenna, a voice call ...


2

An ordinary modem will not be sufficient if you want to pass DTMF. If you can't find one that is designed to detect tones, then what you need is the part of a modem called a Data Access Arrangement. It comprises the isolation from the telephone line, audio balancing hardware, hookswitch, and typically a ring indicator for incoming calls. To build your ...


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