So, it’s been 4 months since I originally posted about my new phone system (see here if you haven’t read it). It’s been running this whole time, and pretty much perfectly. I thought I’d take this time to talk about how many telemarketers I’ve stopped, how much money I’ve saved, and some more detail on how it’s built.

Statistics

I’ve received 263 calls in the last 4 months. That’s an average of 16 calls a week or about 2 calls a day. Now, of course, it isn’t that perfect. The highest is 10 calls in a single day. So, not huge, but respectable for a 2-person house with no children.

Since I set it up to automatically route known people in, and send the rest to voicemail, I can get a more detailed breakdown. Of the 263 calls, 127 of them were people I knew, but 136 (51%) were sent to voicemail. The 136 were from 57 unique phone numbers, of which only 22 actually left voicemail. That means that 114 calls were people (or machines) who had nothing important to say, and that I didn’t have to listen to. That’s a pretty good time wastage reduction to me.

Costs

There are basically 3 “monthly” costs to this system. The VOIP provider, the Telephony provider, and my server time. As I have been running this on my server in my house, that was effectively $0.

Month	VOIP	Telephony	Total
July	$3.41	$4.45	$7.86
August	$2.57	$4.10	$6.67
September	$2.71	$4.60	$7.31

Because I use a VOIP adapter (Obihai) that supports multiple VOIP providers, I have one VOIP provider for outbound (voip.ms) and a separate one for inbound SIP (linphone). The inbound one doesn’t charge me, so my VOIP bills are only for calls that I make. I’ve been quite happy with voip.ms so far. They charge $1.50/month for 911 services, $0.85/month for a phone number, and $0.009/minute (I’m using their premium services since I feel the phone quality is better). That’s anywhere in North America, so there is no such thing as long distance charges.

The telephony provider (Twilio) provides all the services I need to build the system. They charge me $1.00/month for a phone number, $0.0085/minute for inbound calls, and $0.004/minute for outbound VOIP (and since linphone doesn’t charge anything for inbound, that’s it).

Considering that my monthly bill from my local phone provider is $34.78, only having to pay $6 to $8 is a huge savings.

Of course, I’m paying both at the moment, since I haven’t pulled the plug on my “old” landline while I’ve been testing the system, but I think I’ll be doing that within the next month or so. There doesn’t seem to be any reason not to.

High Level Architecture

Some people have asked for additional details on the design. I’ll probably write a Part 3 post in the future going into the details, but I thought I’d provide some basic details. NOTE: This will only be interesting to the tech-heads; everyone else can skip.

Whenever a person calls my main phone number, it’s answered by Twilio (#1), as they are the Telco for the number. Twilio looks up the details on that phone number, and sees that I want it to issue an HTTPS (REST) request to my server (#2). As a side note: If my server is not responding or provides an error, Twilio has a fallback where it immediately sends the call to my cell phone. Thus, if there are any technical glitches, I still get the call.

At this point, my application, Phonely, receives the request. It queries against the database (#3), which is currently PostgreSQL, to figure out how to handle the call. If the phone number is not listed, or does not have ‘direct’ contact privileges, then the Phonely server begins the process of collecting voicemail. This occurs by a bunch of back and forth requests between Twilio and the Phonely server, using Twilio’s great XML language, Twiml, to make it happen.

As an example of this, here’s the first response Phonely returns to start the voicemail process:

<Response>
    <Gather timeout="5" numDigits="1" action="https://phonely.example.com/twilio/voicemail/StartCaller?DQ-Submit=true" method="GET" finishOnKey="#">
        <Say language="en-US">Hi. Hold on, this is not a normal answering machine. I screen all calls from unrecognized numbers, therefore you won't reach Mike without leaving a message. Stay on the line or press 1 to leave a message.</Say>
    </Gather>
    <Redirect method="GET">https://phonely.example.com/twilio/voicemail/StartCaller?DQ-Retry-Count=1&amp;DQ-Submit=true</Redirect>
</Response>

In this fragment, we’re telling Twilio to read some text back to the caller and attempt to gather some keypresses. If they press a button, then it will call Phonely back with the keypress. If they don’t do anything within 5 seconds, then it will call Phonely back indicating that they didn’t press any key.

It’s a very straightforward language, and can be easily used to build very complex responses.

Once Phonely has decided the next course of action, it also issues a request to my XMPP/Jabber server (#4). XMPP/Jabber is an instant messaging service that underpins alot of systems out there (Facebook Chat, WhatsApp, Google GTalk, Playstation chat, etc.). This message is directed at an app installed on my phone (#5), so I get immediate notification of whose calling. If they leave voicemail, then I also get the voicemail so that I can listen to it directly on my phone without having to call anything. Additionally, it can send to multiple parties, so everyone at the house receives the message on their instant messaging apps.

If Phonely decides that the person is allowed to directly contact me, then it sends a response to Twilio commanding it to redirect to my SIP address. SIP is the underlying protocol for connecting with VOIP phones. Twilio then connects with my SIP provider, linphone.org (#6), which then redirects to my actual VOIP adapter at my house (#7). All my cordless phones are connected to my VOIP adapter, so my phone then ring (#8), I answer, and we have a conversation.

If I decide to make a call (#9), the VOIP adapter issues the outbound connection to my VOIP provider (#10), who then connects to the real phone number (#11).

Personally, I’d like to simplify a bit and remove linphone.org and voip.ms. Not that they haven’t been providing a great service, but I should be able to get Twilio to provide it all, and that would just make the system simpler and less error-prone. I just haven’t figured out the details yet.

As always, feel free to leave questions in the comments or contact me at blog@michaelmansell.com

I’m sure we’ve all experienced the never ending calls of telemarketers. Especially around dinner time.

My wife and I have had the same phone number for more than 20 years, and more than a decade ago, we did provide some donations over the phone (although now, all our donations are done through a single institution). That means that we’re on a large number of lists. It’s not uncommon to receive 10+ calls a day.

As I’ve recently retired from the corporate scene, I decided to do something about it. After about a month of development, I’ve come up with “Phonely” (yeah, I might need a better name). This is an application that leverages the Twilio API (although it should be easy to adapt to Plivio, Nexmo or similar systems) to provide a complete phone system.

In a nutshell, I ported my phone number to Twilio and registered my application with them. Therefore, as soon as a phone call comes in, Twilio calls my app. My app looks at the incoming phone number, and checks it against a database of numbers. If it’s recognized and approved, it immediately forwards the call to the house phone (via VOIP). If not, it sends them to a voicemail system (also part of Phonely).

Thus, for friends, family and known companies, it works just like before. They dial the phone and it rings in the house. For everyone else (aka telemarketers), they go to voicemail, and my phone never rings.

The fact that I’ve now got a computer answering the phone, there’s a whole bunch of other stuff I can do. For example, I can have different voicemail prompts for different people. Another example, if the same phone number dials multiple times in quick succession, I can forward it to the house phone (telemarketers don’t dial back that quickly). Thus, people dialing from numbers I don’t recognize can still get through by just redialing right after getting voicemail.

Another feature I’m playing with is to have the ‘forwarded call’ actually travel with me. If I’m at home, it rings the house phone, if not, it rings my cell (a small app on my house network periodically checks if my phone is on the local network, and if not, tells Phonely that I’m away from the house).

Overall, this has basically cut out all telemarketer calls, since almost none will leave a recording, and even if they do, I’m not disturbed.

Additionally, switching over to a VOIP system from my local phone provider (Telus) seems like it’s going to save me a bunch of money.

I currently have a pretty basic landline package, but it’s still $40 CAD a month. With Twilio, the phone number costs me $1 a month plus about $0.01 / minute (it’s a little fluid, as for voicemail calls I only have to pay $0.008 / minute, since it’s just an incoming call, but for the real calls, I have to additionally pay $0.005 / minute for the outgoing connection, so it could be up to 1 cent a minute.

However, even at $0.01 / minute, that still means that I’d have to have more than 3900 minutes of calls to break even with my old landline. As that’s 65 hours or more than 2.5 days straight on the phone per month, I know that I spend nowhere near that much time on the phone.

At the moment, I’m just using this system for myself, but I’m thinking of making the entire system available as open source (probably via a Docker image). I’ve even thought about running a small business to make it easy for others to use (even with Docker, you still have to have the technical know-how to run Docker, have a server to run it on, setup and configure the Twilio system, and likely setup a VOIP phone at home).

I’ll likely provide some additional blog entries on some of the technical components of the system in the near future. But I’d love to hear anyone’s feedback or comments.