Pierre’s Lab

Just finished testing my email2phone system I didn’t invent it as it exists since a year or so. The feature is quite simple. You send an email or SMS to a server who connects a long distance or international call to a phone.

Great when you can’t make international calls from the office or cell phone or better yet from hotel rooms.

For example you want to call +44 55 55 55 55 55 from your office 952 555 5555. Service providers ask you to SMS or email a message like ‘password’ call 011 44 55 55 55 55 55 from 011 1 952 555 5555 then to reply to a SMS or email confirming the call… quite secure.

Using my Asterisk IP PBX is to create table of authorized requestors, no needs for passwords and verification. It also allows me to automatically route the call without specifying the destination and to create shortcuts:

• If I email from my office, I just send and email with the destination number, my office phone rings within 30seconds with my correspondent. I want to call my Dad, I just email with ‘Dad’ and 30 second later my Dad is on the office phone.
  Same using my cell phone.
• If I send a request the call is transferred to my cell. Normally it is where want the call.
• If I need the call to be transferred somewhere else I just email/SMS: ‘destination number’/’transfer number’ et voila!

Simple, easy and safe!

That’s the question. Power over Ethernet (POE) technology is a system to transmit electrical power to remote devices over standard twisted-pair cable in an Ethernet network. Power is transmitted along with data.

The technology is comparable to POTS telephones, which also receive power and data (although analog) through the same cable. It works with an unmodified Ethernet cabling infrastructure.

POE is ‘organized’ by IEEE 802.3-2005 and provides 48 volts DC over two out of four available pairs on a Cat3/Cat5/Cat6 cable with a maximum current of 400 mAmp for a maximum load power of 15.4 watts.

The big advantage of POE is that you don’t need to power the remote equipment. This is perfect for IP phones or surveillance IP Cameras. The big down side is cost. IP phone are some 10% more expensive which is not really bad unfortunately, switches and routers get a hike up to 150% compared to non POE.

If your network includes many remote units where power can be difficult to setup, POE is the way to go.

The common standards are Session Initiation Protocol or SIP, H.324, H.323 and proprietary solutions - the most know being Skype.

H.323 and H.324 are multimedia standards designed to provide converged services - video telephony services, voice and data.

SIP is the standard for basic voice over IP calls - Vonage desktop uses SIP. There are several standardization groups working on bringing these standards together.

Often for a home user, proprietary solutions like Skype are the only solution. Small and large business will go with SIP, H323 or H324 depending on their needs (Voice, Video and Data).

The simplest and easiest setup is using one of the available PC-based solutions like Skype, MSN, Yahoo or Vonage. These use almost any PC connected to the internet over DSL or cable. It works on dialup but bandwidth limit becomes quickly an issue.
The PC needs a good quality audio card and speakers and microphone or a headset - which I strongly recommend. Calling PC based members (Skype, MSN, Yahoo) works well and is free. Calling regular phone numbers costs money and/or requires additional equipment. Vonage gives you a 10 digit number in your area with 500 monthly minutes the monthly cost is $9.99. Skype offers Out-calling and In-calling plans which can be expensive - no free minutes.

The next level is the consumer VoIP system designed to replace a single regular phone line. These are offered by many large telephone and cable companies but also by third party such as Vonage. They require an ATA (Analog Telephone Adaptor) connected to your internet connection. ATA extract voice packets and provide a PSTN port for a regular phone or PBX. These routers manage traffic load to handle voice call quality which is as good as a regular land line.

Small business setups can grow to I-PBX solutions. I-PBX have more features than PBX and can cost as much as PBX. Three main solutions exist:

• All IP from end to end. There is no phone line from the Telco but an internet access to connect to the VoIP provider. Moving from an old PBX to an all IP can be costly and even more if the local wired network is old and doesn’t support QoS.
• IP to PSTN, this often a good upgrade solution. The existing PBX is replaced by an I-PBX, the Telco is replace by a VoIP provider but the internal phones network is kept. This solution doesn’t work if the old PBX uses dedicated non-PSTN phones (Rohm, Nortel…)
• PSTN to IP a good phone and switch upgrade solution. The Telco lines are kept and feed an I-PBX. The phone network is replaced by IP phones - this solution can be costly if the local wired network is old and doesn’t support QOS.

AR1688 is a programmable chip, used for low cost IP phones, it replaces the famous open source PA1688. The architecture is the same, with 8-bit controller for VoIP protocol and 24-bit DSP for voice compression algorithm.

If you compare both chips, the AR1688 has more CPU processing speed and higher and better integration. The IP phone based on AR1688 has improved performance, better voice quality, more features at lower cost.

AR1688 specifications and cross reference with the PA1688:

• CPU clock speed: 48Mhz, the PA1688 ticks at 22Mhz
• DSP runs 60MIPS, the PA1688 runs 33MIPS
• Integrated high-quality audio codec, the PA1688 need external codec
• Integrated SRAM, no external SDRAM needed, the PA1688 needs 1×16 external SDRAM
• RoHS ready
• ICMP response time for 1472 bytes: 10ms, the PA1688 response 21ms)
• TFTP server data put through: 140kbytes/s
• MD5 48 bytes encryption calculation: 4.8ms, the PA1688 needs 9.9ms)
• Software API use open source SDCC compiler, the PA1688 uses commercial Keil C51

Bottom line, the AR1688 is faster, better and cheaper to integrate.