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MMI codes & USSD We all have used the *123# kind of service numbers to query our SIM account balance and other services. All these service codes which start with * and end with # are called MMI codes (Man-Machine-Interface) . MMI codes can be broadly classified into 4 categories: Manufacturer defined codes: As the name suggests, these are coded by the manufacturer. For example, *#06# displays the IMEI number(s) of your handset. USSD codes (Unstructured Supplementary Service Data): These are provided by the network operator and involves some direct communication with the network. For example, *121#, *99# and so on... SS codes (Supplementary Service): These codes also involve communication with the network about features like call barring, forwarding. Hardcoded into every GSM/UMTS/LTE device worldwide and cannot be changed by the network operator. SIM Control Codes:  These codes are used, for example, to change your SIMs PIN code, status information, etc.      To know more about

Railways There are a lot of interesting invisible things that are working in Railways. We sometimes discover some of them. I too discovered something interesting about railway track grounding on keen observation.  Single Line Supply We know that trains run on a single line supply i.e, just the phase line from the power station runs through the overhead lines and ground is provided by the rails.  Just to have an idea of current through the overhead line, consider a 3000 HP engine @ 25kV. This means that the current drawn is at least 90A (considering rated load). Ground Resistance Power stations generally have the neutral wire buried deep into the earth to have a very less ground resistance or almost zero ground resistance. But at the load side (train) the rails are laid on the surface. Assume a 10 Ohm ground resistance because of the rolling stock and the rails being laid on the surface. If a 100A current flows through this, there will be a 0.1MW loss from each train running on the tra

Introduction Today I want to share my understanding and knowledge about some of the commonly encountered terms related to income tax and income tax returns. I am sure almost everyone would have encountered a situation of being asked for your PAN by an employer or some entity that is paying you money. Why exactly do they ask your PAN and what do they do with it?   What do they mean by saying that they have "deducted some amount as tax"? How to check or ask for proof if they have genuinely paid the deducted tax amount to the IT department? Though it might not be of great use to everyone to know about these things now, it is always good to be familiar and to realize if you are being cheated by your payer. Like they say- "It is not a shame to be deceived, but it is to stay in the deception" I am not saying that there are cheaters in this country, but you should know what your rights are. So let's get into the topic :) Tax Deducted at Source ( TDS ) You would have co

About India Post India Post is one of the largest postal services network in the world by GoI. We all should be proud of it, be aware of the services provided, and utilize them. Even in this digital era, the need for mailing and courier services is significantly prevailing for authenticity and maintaining records.  There has always been a wrong perception of the reliability of the services offered by India Post for the reason it being a public sector organization. But things have changed and India Post has developed a lot and is striving to keep its services on par with the private companies.  For example, the courier service(letter in an envelope) offered by private companies is equivalent to India Post's Speed Post . It is much cheaper (around 50/-, depends on distance and weight) and as reliable as any private courier service. It also comes with online tracking service too. What more do you want! Apart from mailing services, India Post also provides a wide range of banking and

Ever wondered what you would get when you decode a UPI QR code. This article is all about that so that you can create your own QR to receive payments and will also guide you to make a webpage to receive UPI payments. Suppose you want to receive a payment from someone, you can just share this link with a specified amount to them which will redirect them to a UPI app. So let's begin the show :) UPI QR Once when I decoded a UPI QR using some tool online, this is what I got - upi://pay?pa=somevpa@somebank&pn=My%20Name&tn=yourtext&am=200&cu=INR So using this we can make QR's ourselves by embedding this text into them. Apart from this, there is something more interesting to observe in the embedding. It resembles a web URL, something like -  https://pa1tech411.blogspot.com/2020/04/upi-qr.html?t=100  with payee VPA, name, message, and the amount being the URL variables. Making your UPI payment link Since it resembles a URL, what happens if we browse it?