Black Box 202T specifications Overview, These modems have many uses

FEATURES

An industrial application for the Modem 202.

•Compatible with the Bell 202T standard.

•Operate over 2- or 4-wire voice-grade leased or private lines.

•For point-to-point or point-to-multipoint polling networks.

•Prevent data and carrier-detect errors over noisy lines.

•Anti-streaming capability.

•Choose between AC- and DC-powered Modem 202T models.

	Modem 202		Modem 202
RS-232	(MD845A-R2)
cable			(MD845A-R2)
Programmable logic		Dedicated wire
controller		pair(s)
		RS-232
		cable
		Remote
		telemetry unit	Water tank
		(RTU)

Modem 202

(MD845A-R2)

Dedicated wire

pair(s)

RS-232		RS-232
		cable
cable
		Remote
Remote
		telemetry unit
telemetry unit	Water tank		Water tank
		(RTU)
(RTU)

OVERVIEW

Back in the day, Bell 202 was the top-speed modem standard, boasting 1200-bps rates that were four times faster than the poky Bell 108 standard. Still widely used in many industries, Bell 202 modems like our Modem 202 or Modem 202T keep data moving along. Order one of these modems to expand an existing industrial, System Control and Data Acquisition (SCADA), or metering application, or to replace an old UDS/Motorola® 202T Modem. In fact, the Modem 202T is a pin-for-pin, form, fit, and function replacement for that tried-and-true modem. Just think what it can do for your legacy system!

The Modem 202 (MD845A-R2) and the Modem 202T (MD1970A, MD1970A-DC) function the same way. However, the Modem 202 supports speeds up to 1200 bps over unconditioned lines; the Modem 202T supports speeds up to 1800 bps over conditioned lines.

Widely installed and a prerequisite for many leased-line applications, both the Modem 202 and the Modem 202T support voice-band frequency shift keyed (FSK) modulation within asynchronous point-to-point or multipoint systems that use voice-grade 2-wire, half-duplex or 4-wire, full duplex dedicated or leased lines. These can be loaded or unloaded circuits, equal to or better than the ITU (formerly CCITT) M.1020/1025 or Bell 3002 leased lines.

These modems have many uses.

You can use a Modem 202 or Modem 202T with remote terminal units (RTUs) and programmable logic controllers (PLCs) to control and monitor a large number of remote devices—traffic control lights, for instance. In addition to SCADA applications, the modems are quite useful for

temperature and pressure controllers in numerous industries, particularly those in which you expect to add automated devices.

The water-treatment industry prefers the Modem 202 because it’s compatible with battery systems from 11 to

18 VDC. The Modem 202 is also relied upon heavily by the U.S. Government for daily commerce.

Noisy lines aren’t a problem either. The Modem 202 and the Modem 202T have circuitry that prevents data errors that occur on such lines, particularly those within multidrop systems where carrier turn-offs and other modems on the same line can cause noise spikes and other harmful high frequencies. The modems combine soft-carrier generation and soft-carrier detection as well as a signal-noise-ratio (SNR) detector to eliminate such line-noise errors.

The modems also have antistreaming features, which prevent them from remaining in Transmit Mode when they’re not actively transmitting data. Great for multipoint applications, antistreaming prevents a malfunctioning

slave modem from occupying the line indefinitely. When anti- streaming is active, the Modem 202 or Modem 202T can only transmit data for up to 56 seconds. Then, they automatically turn off their transmitter and look for an ON-to-OFF transition of Request To Send (RTS) before proceeding with normal operation.

Modem 202T offers diagnostic testing features.

For testing purposes, the Modem 202T has a five-position rotary switch on its front panel for running analog and digital loopbacks as well as self-tests. To verify the transmitter and receiver of the local modem and its connection to a local DTE,

8/22/2007	724-746-5500	blackbox.com
#16407

2 of 3