PSTN Telephone Modem

PSTN Telephone Telemetry Overview

The PSTN Telephone Modem connects to the Public Switched Telephone Network (PSTN) through a standard twisted pair phone cable connected to a phone jack. Modems can be either internal or external to the CPU of a computer or data logger. Sometimes the modem is attached directly to the logic board. Other times, the connection is made externally through a port. The port configuration is based on the RS-232-C standard, where the connector consists of 25 pins. Frequently, only a subset of the standard pins is actually built into the connectors. An 8- or 9-pin connector will work just fine, simply using the pins for the more frequent commands. As long as there is a wire each for sending, receiving, and ground, the connector will function.

Advantages to PSTN Telephone Modem

  • No antenna
  • Straight forward, well establish technology
  • Easy to set up and maintain
  • Auto-dail and auto-answer capability
  • Flexible "AT" command set
  • Two-way communications
  • Event notification through one or more stored telephone numbers (such as pagers, internet, cell phone, etc.) to provide a timely warning.

Disadvantages to PSTN Telephone Modem

  • Requires a direct phone line connections
  • Monthly service fees

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