house alarm systems and the fixed phone line

[polarized]

scantronic standard dtmf 2300 hz

Hello,

Some of the alarm systems use a phone interface to the main center, so in the case of an alarm event the system can notify the company which provides the service of guarding the object. I am interested if the phone interface inside of systems like this is a real analog modem on a dialup line(POTS) or the communication used in systems like this is by DTMF tones, or maybe another way?


Regards.

 

[flatulent]

phone line emulation

Two systems that I have seen for home use have a voice recorder. It phones a list of numbers and plays the recording. The directions say to ask permission for those to be phoned and to have the recording state your name and address and the fact that the arlarm has beeen triggered.

 

[Mr_Programmer]

The phone/modem is quiete simple, at my actual project the for the components are round about 1,50 USD. The signalling is done simply via PIC µController at 4MHz for generating DTMF and transmission signals.
There exist some standard protocolls with a transmission speed of 10baud. Really easy to handle for a PIC, Atmel ... what ever.

 

[jss]

Hello polarized,

There are basically three systems, with small variants:

The oldest and simplest, but still broadly used, "Ademco slow or fast" uses a clone decadic dialing in which the spaces (interruption) are replaced by 1900 Hz tones because you obviously can't interrupt the line during the connection. The marks are silent. You then transmit a 3 digit customer code followed by one digit of alarm code (3/1 format) or then a similar 4/2 format. Slow means digits are transmitted at 10bps whereas fast is 20bps. This information is transmitted until the receiver, after receiving 3 equal rounds, sends a kissof tone usually of 1400Hz but can be 2300Hz on some variants.

There are then some DTMF codes like ContactID (Ademco) or Scantronic Fast and some FSK like Silent Knight or SIA.

Spending some extra time I could find some more information if you really need it.

Enjoy
JSS

 

[artem]

It is also easy to implement voice playing :
Write (PCM encoded could be without a or m compression ) voice into eprom and scan desired address there for needed announcement dependent on sensor triggererd

 

[polarized]

ADEMCO coding

Hi jss,


I have read your post regarding the ADEMCO coding sequences on fixed telephone lines for alarm systems. My question is: is this a standard telephone dial up line, not a leased line, where the transmitter dials the telephone number he wants to call, then the telephone main switch establishes a audio path to the other end, as it would do in a regular audio voice call and then the communication by special tones begins. The same question stands for the DTMF and the FSK variant of alarm systems. The coding systems do not matter too much for me as long they use the standard dial up analog telephone line(POTS) and the standard audio band 300Hz to 3400 Hz.


Regards.

 

[abb652]

Ademco DTMF FSK

Hi.

All of them uses a standard telephone dial up line in the standard audio band. (300Hz to 3400Hz)
(Like a PC modem or a Fax.)
In general the alarm systems dont use signals out of the audio band because they interfere with xDSL modems conected to the same line.

 

[jss]

Ademco alarm report format

Hi polarized,

Sorry for the delay, took some days off.

Unfortunately my poor knowledge of the English language makes me often misunderstood. Actually, if you look through my posts you'll see that it already gave me very unpleasant situations.

Unlike for me, it seems to be your birth language so I'll do my best to make myself clear. Here it goes:

An "Alarm dialer" (Industry terminology) has several input trigger channels, usually dry contact inputs but can be voltage actuated on some models. Please note that this "dialer" can be integrated in the alarm control panel, even driven by the same microcontroller.

It also has an input for the outside telephone line (PSTN) that, after crossing the double contacts of the line deviating relay, exits through the terminal block to the in-house phone network.

Upon an alarm, the outside phone line is then deviated from the house network to the dialer. This also cuts any ongoing conversation. After a short pause another relay, the line seize relay or an electronic current steering network, seize the line and listen for a dial tone. This is usually programable to "blind" dial.

The Alarm Monitoring Station telephone number is then dialed, DTMF or decadic (pulse) and the dialer listens for a handshake tone coming from the alarm receiver, 1400 Hz for Ademco slow format and 2300 Hz for other fast formats (DTMF, FSK...), if my memory is still good (As I said before, I can check these values if it is really important for you).

After receiving the handshake, the dialer starts sending out rounds of the alarm report consisting either 3 digits for customer number and 1 digit for channel code (alarm code... burglary, fire, medical ...) which is format 3/1, or then a similar 4/2 format. These digits are transmitted as a number of bursts of 1900Hz, the number corresponding to the meant digit where "0" is ten bursts. The timing is the same of a decadic (pulse dialing) where the "space" (open loop) is replaced by the burst and the "mark" (closed loop) is silence. Both these formats can be transmitted at 10 bps or 20 bps assuming that the receiver is capable of receiving both.

After receiving three equal rounds of information in a sequence, the receiver sends a kiss-of tone, which again I believe is 1400 Hz but I'm not sure. Then the dialer disconnects. If it couldn't obtain a kiss-off tone after a given time, it redials a maximum of 15 times, which is the maximum allowed by TBR21.

Hope this helped, if not, you can always "redial"

Keep well
JSS

 

[polarized]

alarm system phone interface

Hi,

I have another question related to alarm systems with analog phone line interfaces:

The alarm system listens for the dial tone and then dials the memorized programable number. The the ringing tone is reproduced for the other side. The alarm side hears the ringing and my question is how does the alarm system side know when to start the voice message reproduction if this is a voice system or if this is an ADEMCO based protocol(with tones) the same question remains. I hope you understand me, when a human dials the number if the other side is free a ringing tone will be present. Then when the other side picks up the phone, he starts to speak. How does the alarm system conclude that the calling side picked up the phone(off hook) state, or it does this in a blind kind of manner? The same question remains with a DTMF based signalling system. One of the answers to this question is the polarity change of the DC voltage present on the analog line.This is related of course to the TELCO owner of the main telephone switch. Is there another way to perform this signalling?

Regards.

 

[Mr_Programmer]

You can recognize the ring tone.
When the tone is gone the phone is picked up, or you will have a busy tone on the line.

 

[jss]

Hi polarized,

Concerning voice communicators handshake, Mr_Programmer is right, that's how it's done. The kiss-off is not so linear, some communicators redial the same number a programmed number of times, some wait for a DTMF code that the user must key a digit code on the receiving phone to stop redialing.

Voice communicators are not used professionaly. An Alarm Monitoring Central Station usually only receives digital communicators (Ademco or not)

Concerning digital communicators, once again my knowledge of the English language seems to prevent you to understand what I mean. On my previous message see the paragraph that says:

The Alarm Monitoring Station telephone number is then dialed, DTMF or decadic (pulse) and the dialer listens for a handshake tone coming from the alarm receiver, 1400 Hz for Ademco slow format and 2300 Hz for other fast formats (DTMF, FSK...)

Keep well
jss

 

[abb652]

Anyone knows if i can use a standard cellphone with the alarm?

I want to build a circuit that detects when the fixed phone line fails and then use the cellphone as backup.

THX

 

[polarized]

analog phone line emulation

Hi Jss,

I have read your post again and now it seems logical to me regarding the handshake tone and the communication start detection. And by the way your english is excellent. Abb652, you say that you are trying to build a backup cellular system in case the analog fixed line fails. I am trying to build something similar, not a backup system but a system that simulates the fixed analog line. In reality it is a cellular system. I am trying to emulate a fixed phone line, so that the alarm system works as usual. Here are some hints: you need to generate a "false" 400Hz dial tone, so the alarm system knows he can dial, you need to pick up the DTMF number tones in case of an alarm event with a tone decoder, so you can later dial them with the ATD number command on a GSM modem, you need to generate a "false" ringing tone, you have to design a 2wire to 4wire hybrid circuit, you have to place an microcontroller who will guide the whole emulation process, you have to connect your circuitry to the audio transmit and receive path on the GSM modem side etc... I am in the process of designing all of this. And, i nearly forgotten I have an additional question: is it necessary to have an DC voltage component to be present on devices which have an interface to the fixed telephone lines, if the device itself does not have electret microphone, like the ones in standard telephones. For instance this can be an alarm system, or a modem or a voice automated machine etc...
This is important to me because I have to know this in case I have to emulate this situation on the fixed line.


Regards.

 

[Fragrance]

Try This

Hi


Try out This remote Alarm system may be you are looking for this

Regards
Fragrance

 

[polarized]

analog phone line emulation

Hi,


This is good if you want to build your own alarm from the begining, but what if you just want to adapt an already present home alarm intended for the analog fixed phone line without any intervention in the alarm hardware and without any knowledge in the data communication flow? Then you would need a device which would emulate the analog line and "bridge" everything to the GSM network.



Regards.

 

[jss]

GSM communicator

Hi polarized,

Now I understand your purpose.
It's already done commercially. Take a look here https://www.dualtech.se
This is one amongst many others.

To abb652: If you are going to use any form of coding that uses tone/silence combinations, like Ademco format for instance, don't forget GSM compresses silence pauses and I know that decompression is not reliable and affects decoding. FSK or DTMF works OK. Just a warning.

Enjoy
jss

 

[abb652]

Hi polarized and jss.

I trying to design the same thing, with the only difference that it works only if the fixed line fails.
I know that it is already done commercially but the problem is that the GSM service providers in my country doesnt allow the use of such devices with an embedded GSM module.
I dont understand why!!
They told me that i can use a standard cellphone like a Motorola ST7867 or Nokia 5120.

Thanks both of you for the hints, i'll post my advance.

Regards

 

[polarized]

GSM compression and decompression

Hi Jss,

You have mentioned that the ademco coding which uses tones and silence periods may have problems when transmitted through the GSM network. What kind of problems? If I understood you correctly the audio signal which is transfered through the GSM network is modified, especcially the silence periods and the decoder on the other end can have problems. Can you explain this strange phenomen of altering the audio in a few sentences? Is there an solution to this problem? You also say that the DTMF and the FSK systems do not have any problems. Is it because they do not use silence periods as a way for transfering data, but only a continuos burst of different tones or group of tones?


Regards.

 

[abb652]

Hi polarized.

Jss please correct me if im wrong!

The GSM speech encoder compresses the silence periods in order to reduce the bit rate, it is done normaly by discontinuous transmission or using SID (Silence Descriptor) Frames.
I dont know exactly how this compression affects the coding but I guess that it could be a timing problem, because the receiver is simulating the silence.
DTMF and FSK do not have any problems because the data is transmitted in different tones (DTMF) or by a continuous burst (FSK).

 

[jss]

Hi polarized and and abb652 (we are monopolizing this thread)

Yes, both of you are right, as much as I know. The problem lies on the incorrect timing of silence periods after decoding.

Actually I've never tried it but I know that the security industry had a lot of problems transposing the Ademco standard to GSM. I think they gave it up alltogether.

This is not a problem once most receivers are compatible with ContactID, another alarm communication standard from Ademco, which uses DTMF. The problem is that it's a bit more complex, it uses 256 different alarm codes.

There's also another standard worth to look at, this is SIA which stands for Security Industry Association.

Let me know if you really need some more information on this.

Keep well
jss