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Engineering Projects

Telephone Triggered Switches


Published on Dec 05, 2016

Abstract

How would you like to be able to energize any electrical device in your home., from any where in the world. and do it without paying for a telephone call? You can do it and it's perfectly legal. With the Telephone Triggered Switches you can do just that. The device described here is a circuit, which responds to the sound of the telephone Deli There is no need to make any hard wire connections to the telephone line, and it is this feature which permits you to build and use this device without any permission from the Department of Telecommunications.

You can't even be charged any tariff for using it in these days of high energy costs, it would be economical to turn off the air conditioning or the hot water geyser before you leave the house, and turn it on an hour before you arrived home. It could be used to turn on the lighting in the house, at night, before you return home.

Introduction

The TTS is a fairly precise device that would find a use in many a home. It basically consists of circuitry that detects the telephone ring, which then is passed on to the Counter & decoder Section which keeps a track of the number of rings received. Upon the reception of the rust ring, a ninety-second timer is triggered. The, Whole -operation should be completed within this 90-second period or the entire circuitry is reset.

Two devices can be connected to the TTS. The first device can be activated by calling the telephone number and terminating the call after 2 rings. The same telephone no. has to be called again after a gap of 25-40 seconds and then allowing for 2 more rings, following which, the call has to be terminated. For the second device to be activated the sequence o be followed is 2 rings, followed by a 25-46 second gap followed by 4 more more rings. The gap between the two sequences of rings should not fall short of 25 seconds, else it may reset the TES.

After the second ring is received, the 25-second timer is triggered. If a third ring were received before this delay is over, the TTS would reset. This precautionary measure prevents accidental activation of the devices connected to the TTS

Upon the completion of the 25-second delay, the third and fourth rings are received. When the 4th ring is received the 25-second timer is triggered for the second time. The relays for the two devices will be activated only after this 25-second delay. This is again a precautionary measure, since if the TTS were to receive more than the specified number of 2 rings (for device 1) or 4 rings (for device 2), the relays will not activate.

If, after the 25-second delay the decoder shows a total of 4 rings, then relay 1 is energized, which in turn activates device 1. Or if a total of 6 rings were received device 2 is activated by means of relay 2. After the completion of 90 seconds the ITS is reset, but since the relays used are of the double contact type the connection of the device, to the 230 volts mains, does not break. So the device remains on once it is activated by the TTS.