Industrial PSTN and Leased Line Modem

TD-36 485 AV
This product is no longer being sold and might not be supported. Product has no replacement part.


✓ Legacy remote access solution

• Traditional AT command modem with 2/4-wire lease line support
• Up to 11 bit RS-232/RS-422/485 to 115.2 kbit/s
• V34 with fast connect, V32bis, V22bis, V23HDX/FDX +multidrop support

✓ Robust industrial solution for long service life in unmanned locations

• Extended temperature –25°C to 70°C (–13°F to 158°F)
• Extensive EMC approvals and tri-galvanic isolated interfaces
• Watchdog and remote configuration

✓ Secure and resilient non internet based remote access

• Secure call back and access
• Caller ID presentation and answering
• PSTN backup for Lease line

✓ Easy to use

• I/O, DTR and data dialling
• DIP switch configuration and TD-tool configuration software
• RS-232, 9-pin D-sub and screw terminals


The TD-36 485 is an industrial modem designed to allow cost effective and simple remote access to legacy serial industrial equipment. The AT command driven modem is capable of synchronising with a wide range of traditional modem negotiation standards providing data rates up to 33.6 kbit/s over both PSTN and 2- or 4-wire lease line circuits.

Designed with remote unmanned industrial locations in mind the modem can operate in extremes of temperature and electromagnetic field. The complete galvanic separation of all interfaces ensures earth loops and transients do not interfere with communication. To keep visits to the site to a minimum a watchdog monitors the modem ensuring constant readiness, and remote re-configuration means that changes to settings can be handled without a site visit.

Firewalls are not an issue as data does not use the internet and with call back security it is impossible for either accidental or deliberate access to any equipment attached to the modem. To provide resilience a second line interface allows a PSTN connection to be established in the event of a lease line failure.

The modem is also simple to configure using the Westermo TD-tool software; standard commands can easily be entered and saved configurations downloaded. RS-232 connections can be made using screw connections as well as the standard D-sub. The modem is designed to be connected to devices with no ability to control dialling so special functions like data dialling and DTR dialling are provided to enable these devices to automatically establish connection.

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Technical Specifications

Industrial PSTN and Leased Line Modem
1 x PSTN and Leased Line 300 bit/s – 56.7 kbit/s
1 x RS-232 300 bit/s – 115.2 kbit/s
1 x RS-422/485 300 bit/s – 115.2 kbit/s

Jennifer Mooney-Perrotta

Customer service, Westermo North America

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