RI-27A Glass Body Reed Switch SPST-NO 500MA 140V Equivalent & Substitute Parts

Part Overview

The RI-27A is a glass body reed switch manufactured by Comus International with SPST-NO (single-pole single-throw normally open) configuration. The component operates at 500mA AC/DC with 140V AC / 200V DC switching voltage and 10W rated power, designed for through-hole mounting in relay applications. The RI-27A is classified as obsolete, making substitute parts identification necessary for new designs and ongoing production support. Functionally equivalent and compatible alternatives exist from Comus International and Littelfuse Inc. across multiple product series.

Substiute Parts

RI-27A

Comus InternationalIn Stock: 907RI-27A Datasheet

Current PartRFQ

RI-27GP2025

Comus InternationalIn Stock: 1072RI-27GP2025 Datasheet

SimilarRFQ

MDSR-7-20-25

Littelfuse Inc.In Stock: 2004MDSR-7-20-25 Datasheet

DirectRFQ

MDSR-10-20-25

Littelfuse Inc.In Stock: 2411MDSR-10-20-25 Datasheet

SimilarRFQ

MDSR-10-25-30

LittelfuseIn Stock: 1233MDSR-10-25-30 Datasheet

SimilarRFQ

MDSR-10-30-35

Littelfuse Inc.In Stock: 1806MDSR-10-30-35 Datasheet

SimilarRFQ

MLRR-3-17-23

Littelfuse Inc.In Stock: 1091MLRR-3-17-23 Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitute selection for the RI-27A is determined by maintaining compatibility across three critical parameter categories:

Electrical Parameters (Must Match or Exceed):

• Circuit configuration: SPST-NO (required for direct functional substitution)
• Voltage switching capability: 140V AC / 200V DC minimum
• Current switching capacity: 500mA minimum (AC/DC specifications must accommodate application requirements)
• Power rating: 10W minimum

Mechanical & Physical Parameters (Must Match or Be Compatible):

• Mounting type: Through Hole
• Termination style: Axial
• Body type: Glass Body Reed

Thermal & Environmental Parameters:

• Operating temperature range: Must cover application requirements within -55°C to 125°C envelope
• RoHS and REACH compliance status

Substitute parts fall into two categories: (1) Comus International RI-27 series variants with identical electrical and physical specifications but differing operate ranges, and (2) Littelfuse MDSR and MLRR series reed switches meeting all electrical requirements with minor operational timing variations.

Parameter Comparison

Engineering Selection Recommendations

Primary Substitute - Comus International RI-27GP2025: This is the preferred direct replacement for the RI-27A within the same manufacturer ecosystem. The RI-27GP2025 maintains identical electrical specifications (500mA AC/DC, 140V/200V, 10W) and identical physical configuration with through-hole axial termination. It carries active product status and ROHS3 compliance certification, providing long-term supply assurance and regulatory continuity. The narrower operate range (20~25AT versus 20~34AT) requires verification that the target application trigger point falls within this window.

Secondary Substitutes - Littelfuse MDSR Series: The MDSR-7-20-25, MDSR-10-20-25, MDSR-10-25-30, and MDSR-10-30-35 variants provide electrical compatibility across the 140V/200V switching voltage and 500mA DC current envelope. These components feature active product status and ROHS3 compliance. Key differences include reduced AC current rating (350mA AC versus 500mA AC) and minor operational timing variations. Operate range selection (20~25AT, 25~30AT, or 30~35AT) must align with application magnetic field trigger requirements.

Higher-Power Substitute - Littelfuse MLRR-3-17-23: The MLRR-3-17-23 provides superior current-switching capability (700mA AC / 1A DC) and increased power rating (20W versus 10W), suitable for applications requiring enhanced switching capacity. Operate range (17~23AT) accommodates lower magnetic field trigger points. This selection introduces increased physical size and weight compared to the RI-27A.

All substitute candidates maintain RoHS3 and REACH compliance certifications with ECCN EAR99 classification, ensuring regulatory alignment for new design releases.

Frequently Asked Questions (FAQ)

Q: Can RI-27GP2025 directly replace RI-27A in existing designs? A: Yes, the RI-27GP2025 provides direct functional and mechanical substitution with identical electrical specifications and through-hole axial configuration. Design verification is required only if the existing application operates with magnetic trigger fields outside the 20~25AT range.

Q: What is the key difference between Comus RI-27A and Littelfuse MDSR series substitutes? A: The MDSR series specifies differentiated AC and DC current ratings (350mA AC / 500mA (DC)), whereas the RI-27A rates 500mA uniformly across AC and DC operation. Applications limited to AC operation may require current derating with MDSR alternatives.

Q: Are the Littelfuse MDSR variants physically interchangeable with RI-27A? A: Yes. MDSR-7 and MDSR-10 series maintain identical through-hole axial termination and similar overall dimensions (1.590" length) to the RI-27A (1.811" length). Physical substitution is compatible; electrical performance characteristics must be validated.

Q: What is the operate range (AT) parameter, and how does it affect substitution? A: Operate range specifies the magnetic field strength (in Ampere-Turns) required to reliably close the reed switch contacts. Selection must align with the application's magnetic bias source characteristics. The RI-27A operates within 20~34AT; the RI-27GP2025 operates within 20~25AT; MDSR variants offer 20~25AT, 25~30AT, or 30~35AT options. Selecting an operate range outside the application's magnetic field envelope will result in non-functional performance.

Q: Why is the MLRR-3-17-23 recommended only for higher-power applications? A: The MLRR-3-17-23 carries 20W power rating and 700mA/1A current capability, compared to the RI-27A's 10W and 500mA specifications. Applications requiring switching capacity beyond 500mA or power dissipation beyond 10W benefit from this enhanced specification. Conversely, standard 10W applications do not require this upgrade.

Q: Are there packaging considerations when selecting substitute parts? A: Yes. The RI-27A was supplied in standard bulk packaging. Substitute parts carry varying packaging formats: RI-27GP2025 (Bulk), MDSR-7-20-25 (Bulk), MDSR-10 variants (Box), and MLRR-3-17-23 (Bulk). Procurement volume requirements and supply chain logistics may influence packaging selection, but electrical and mechanical compatibility remains independent of packaging format.