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Portable Message Waiting Indicator (2000)

Remember voicemail?  Consulting to free online Voicemail provider eVoice in the spring of 2000, I was tasked with a problem: customers were complaining that their phone lines and phones were not flashing to indicate that they had new voicemail waiting.  Looking into the access networks to provide equivalent service to deliver stutter-tone via the Regional Bell Operating Companies (RBOCs) I discovered the cost was prohibitive: it was tariffed at approx. $2 per line, required costly direct network connectivity, and had to be provisioned via a patchwork of relationships with each individual RBOC.  This led to exploration of alternatives.

To be successful, a solution had to achieve the following goals:

  1. Be user-provisioned (or otherwise easily provisioned)
  2. Cost less than $1 per month to operate
  3. Provide visual indication of new voicemail pending

I designed the Pocket Message Waiting Indicator (PMWI) device as a viable alternative that could function at a fraction of the cost of alternatives.  A benefit, since the device used the POCSAG paging network for signalling, was portability.  Hence, the addition of a keyring loop.  As originally designed, the device would measure 4CM x 4CM, and approximately 1.2 CM thick and cost about $13 to manufacture.

Signaling the PMWI was simple: it received a message to turn its light ON, or OFF. During design I determined that wireless over-the-air may be the cheapest means of signalling a remote device, versus using the PSTN.  POCSAG networks were being maintained by wireless carriers in order to support legacy paging devices, but were largely under-utilized — which led to favourable pricing.  I further reduced the PMWI’s network cost by bundling up to two dozen notifications into a single pager message, meaning that hundreds of PMWI devices were clustered on a single device ID, monitoring the same namespace.  This had several benefits:

  1. All devices were “on” by default, and could be associated with a user’s account via the eVoice web site. Apart from removing a plastic battery strip which kept the device from draining its battery on the shelf, no provisioning was required.
  2. Each user device could operate at a cost of <$0.19 per month
  3. Users could associate multiple devices with a single account, allowing eVoice a high-margin up-sell opportunity
  4. PMWI devices could be sold in stores as a key marketing tool for eVoice
  5. By clustering messages and devices, and by spacing the radio checkin interval substantially, radio battery consumption was reduced

In so many respects, PMWI notification devices were better than what you could get from the local phone company: you could know when you’d missed a call and had a message wherever you went, and this didn’t depend on a mobile phone or internet connection.

For this work I was awarded US PATENT #7477729B2.


Posted on

November 16, 2000