Telephone modems are affordable, portable PC telephony systems, widely popular among internet users to make calls. There are two ways you may connect to make distant modem calls from your PC to a telephone: one is the voice mode, and the other is the data mode. It is important not to mix the PSTN and ADSL modem connections of the hardware. Similarly to a telephone, the modem dials the number of the subscriber to the PSTN network. You are always connected to your ISP with an ADSL modem. With your IP address, you can connect to other IP addresses. You can call with a hardware like an ADSL Modem from a computer to a phone by leaving the IP network and going back to RTC but the cost will be charged to your phone on the CTS.
With a 33 or 56Kb/s modem, to connect, it dials the phone number of a subscriber to the PSTN network, just like a telephone. The recipient may be a telephone, FAX, another modem, providing the actors (and call) speak the same language (protocol). And on the CTS, the cost will be charged to your phone...
With an ADSL modem, you are permanently connected with your ISP; you are assigned an IP address and connect to other IP addresses on the internet. The ADSL modem is more akin to a "network card" that a modem with respect to the connection.
With a modem RTC, for example you could connect directly to another PC (your home or house) and remote start with a simple phone call, interest standard ATX!
Anything that connects a conventional phone is the CTS network and uses the low frequency (voice), the ADSL modem connects through a filter that only passes frequencies that ADSL (and isolates equipment CTS).
With a modem, your ISP (you have dialed the phone number) connects to a PSTN gateway / TCPIP that lets you access the internet, but it remains the basis of a dial-up connection!
The phone dialler for Windows allows a classic modem command asking him to make the number for you and that's all. It is still RTC.
The CTS line can operate in 'voice' to call, or in 'Data' connections for modems and fax machines.
- Mode 'Data', the modem transmits fully to the data received from the PC (modulation), and conversely, data from the line to the PC (demodulation).
- Mode 'Vocal', audio signals on the PSTN (your words or the equivalent) are not interpreted by the modem, and therefore are not transmitted to the PC via the USB or serial links, and some models modems (internal cards) have input / audio outputs to relay the audio to the soundcard to use the microphone and speakers of the PC.
Telephone modem CTS
You need a modem with an input/output connected to the sound card (microphone and speakers connected to the PC!). Software (Winphone or others) will allow you to store numbers, numbering, send / receive Fax, etc...
Your PC has become a big phone / fax / phone book, but always by RTC, therefore invoice!
If the called party uses the same software as you (Winphone), digital communication is the more need for sound output on the modem or connection to the sound card software will provide the digital encoding of your voice (microphone) and return of the voice of the corresponding (by HP). Additional advantages, recording conversations, answering machine functions, etc. ... But in this mode, impossible to reach a fix!
Call from PC to PC
Whatever the modem, simply connect to the internet - the audio is digitally encoded.
Many programs allow, Skype, Teamspeak, Winphone, including messengers such as MSN, Yahoo, etc ...
Call with an ADSL modem from PC to phone.
Large interest, since you can reach the world through the Internet ...
Technically, no problem: you must leave the IP network in the vicinity of the person and return to the RTC, thus a gateway TCPIP / CTS (the opposite of that used with a modem) ... but Ouch! billing on the CTS is hefty!
Taiwan if I call this method, the PTT of Taiwan will have to send me a note of the communication between the PSTN gateway TCPIP / CTS and my corresponding Taiwanese since it is the caller who pays for the communication...! !
That is the problem - billing.
However, there are regions where the phone is free (Canada, Florida and others), and in this case, the call to a phone is possible provided that the bridges are in place (but the implementation and services are not free).
There is software for calling a landline, such as Net2Phone, which offers dozens of free minutes as welcome gifts. I've installed and tried several times to call in Canada without ever succeeding in obtaining communication (although this may be due to my config, firewall or other).
Finally, while this is still a little sad...with ADSL, and to reach a fixed or send a fax, you are forced to use a modem ...