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