Two Channel TTL to 24V & 24V to TTL Converters

Calex Mfg. Co., Inc. of Concord, California announces the availability of the Models 8501 and 8502. Each Model contains two independent channels, which accept a TTL, or 24 V pulse signal and convert that signal to a 24 V pulse or TTL output. The 8501 or 8502 is extremely useful when only one signal type is available, ie. a 24 VDC to 5kHz signal, and the receiving device requires a 5 V TTL input. An example would be a Stepper Motor to PLC Interface.

The Model 8501 is a two channel 5 V to 24 V converter. The two independent channels require 7 mA into 382 ohms to provide a 7 mA output into the 3 K, 24 Volt typical PLC logic input. They may be driven by standard TTL logic, H series TTL logic or with
an open collector NPN transistor. Note that low power TTL logic will not drive this unit. The output is a floating optocoupler NPN transistor which may be connected in either source or sink configurations. The input frequency for the 8501 is DC to 15KHz.

The Model 8502 is a two channel 24 V to 5 V converter. Each channel requires 7 mA into 2.5 K ohms to provide a 5 mA sinking output to TTL 5 Volt logic. The output is an optocoupler NPN transistor collector and requires the 5 Volt logic supply and its return. The input frequency range is DC to 20 KHz. The inputs are isolated by optocouplers and are protected from ESD by varistors. The two outputs have a common emmiter with each output collector capable of sinking a minimum of 5mA.

The 8501 and 8502 are housed in a DIN Rail mount enclosure which measures 1.65"H x 1.06"W x 3.78"L. Both models are UL 508 and 1604 recognized. All Calex Signal Conditioning products are backed by Calex's five year warranty. Units are available from stock to 6 weeks. For pricing or more information, contact Calex Mfg. Co., Inc. 925-687-4411 / 800-542-3355 or fax 925-687-3333. For a complete data sheet on the Model 8501 or 8502 go to or email The Calex corporate address is 2401 Stanwell Drive, Concord, California 94520 USA. Calex has manufacturing facilities in both Concord California and Tijuana Mexico.

2401 Stanwell Drive, Concord, CA 94520-4841


(925) 687-4411

FAX: (925) 687-3333


Contact: Michael McNally (

Phone: (719) 266-6046

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