Small intercom system design

[clanofwolves]

Hello,

I'm new to this forum and I hope that I can find some help and not irritate the knowledgeable electronics experts too much with my questions.

A bit of background: I am involved with a group that is doing work on a small private church run school in Belize City, Belize, C.A. and they could really use an intercom system. After pricing new ones and looking into used ones from local school systems, I determined to look into making one.

Can anyone tell me where I can find a design with materials and schematics for a simple intercom system? I have novice electronics equipment and abilities, but I need help.

Thanks in advance. :)

[MP]

Welcome to the forum. Here are a number of links for a wide variety of intercom schematics. Hope it is helpful.




http://www.rcrowley.com/clonecom__schematic.htm

http://www.austriamicrosystems.com/04segments/communication/pdfs/AN2507.pdf

http://www.mitedu.freeserve.co.uk/Circuits/Misc/intercom.htm

http://www.mitedu.freeserve.co.uk/Circuits/Audio/doorint.htm


MP

[mixos]

Also check the ones that are hosted here:

The Original 2 Phone Link Design

This is the updated version of the very first Link circuit that I designed for Silicon Chip magazine here in Oz, back in 1996. It was a bit hardware heavy, (nd therefore expensive for what it would do) having two heavy duty relays and two by two transistor oscillators, for ring tone and ring impulsing. These items have been replaced with optocouplers and an NE 556 dual timer chip, as per the rest of the Link cicuits. It provides for basic communications between two phones only, and there aren't even any numbers to dial.

Project Link: http://www.electronics-lab.com/projects/telephone/016/index.html

The Link Telephone Intercom

This is the original version of the Link circuitry and it employs pulse dialling phones, a simple 2 chip circuita for producing service tones and counting dialled pulses. It uses a four wire circuit between each handset and the 'black box' switcher board, and employs 9 volt DC buzzers in place of the bellset, allowing for portability and battery operation. It would be a great introductory project for hobbyists and junior high school students studying the area of telephony and digital electronics.

Project Link: http://www.electronics-lab.com/projects/telephone/013/index.html


The Link A2B+1 Intercom

This version is more advanced than the original Link design in that it employs DTMF dialling, a simple relay matrix for internal signalling and external connection to an outside Telco line. This version also uses a simple ring voltage generator that actually rings the electronic ringer inside each phone, and a true 'ring trip' circuit that trips the ring and halts the ringer when the called party's handset is lifted up off hook. Useful for light internal and external phone traffic.

Project Link: http://www.electronics-lab.com/projects/telephone/014/index.html


The Link 4+0

This version is similar to the link A2B+1, except that is is for internal intercom use only. The outside line access circuitry has been removed, and an extra two phone handsets have been added. It has one or two extra possibilities, in that remote control applications can be employed, whereas this would be impractical in the original four phone Link circuit. It uses DTMF dialling, and only uses a two wire circuit between phones and the black box switcher board.

Project Link: http://www.electronics-lab.com/projects/telephone/015/index.html

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Designed by Austin Hellier
30 November 2003