• Generally defined as a part of the signalling equipment

• NMŠ and NMŠM relays meet parameters of N Type Relay

according to UIC 736 Standards

• Modular construction

• Small dimensions and weight

• Low maintenance cost

• Easy to exchange during operation (plug-in units)

• Low consumption

General Description

Miniature signalling relays are modular

plug-in elements and because

of the failsafe properties they are

primarily used as switching elements

in the railway signalling technology.

They are a part of the signalling

equipment but they also function

as separate interfaces connected to

any system. According to the construction

they are defined as plug-in

relays and relays for installation as

a relay sets. Usually these relays work

in circuits of 12- 24 V DC. In case

of AC circuits the relay includes also

built-in diode rectifier.

Relay is connected to the function

unit through a socket. Relay working

position is horizontal (±5°), while

the contact blades are in the upper

part of a mother board. Contact

blades are guided into the socket

contact springs by guide pins. Relay

is secured by a fastening screw.

Installation into the outdoor metal

cabinets without protection against

sun radiation in temperature range

−25 to +70°C with relative humidity

of up to 95%.

Basic Technical Description

The contact system and its connection

to the armature is constructed

in such a way when one make-contact

is released all break contacts

are closed and vice versa. Release

of the make contacts and making

of the break contacts is carried out

by the armature weight connected

to a lingoe.

The make part of each break-make

contact is made of carbon (upper

– AgC), the break part of silver

(bottom – Ag) and movable contact

spring is terminated by the silver

contact. The reinforced make contacts

are made of AgCd.

Each contact set consists of make

contacts, break-make contacts

and break contacts, which are connected

to a relay armature over an

insulation material.

Lettering of the relay type is as


N – neutral

O – light (with rectifier)

M – miniature

V (G) – with rectifier

P – with reinforced contacts

Š – plug-in (relay, whose

lettering does not include “Š”,

is destined for relay sets)

M – delayed release (if the letter

is placed at other than

second place in the relay

lettering type).

Letter B behind relay type lettering

indicates safety version of relay with

insulation strength of 4 kV.


Basic Technical Parameters

Load of contacts

Electrical strength

Contact resistance (values without socket)

Mechanical life

Non-simultaneous switching



Ag, AgC contacts

AgCd contacts

coils against ground

contacts against ground

contact bundles to each


AgC – Ag

AgCd - Ag

Ag – Ag

AgCd contacts

with cover

without cover

with cover

without cover

2 A, 24 V DC

0,5 A, 250 V, 50 Hz, resistance load

15 A, 30 V DC

4000 V, 50 Hz

0,4 Ω

0,5 Ω

0,05 Ω

1 × 10 6 contact making

4 ×10 6 contact making

0,2 mm

85 × 110 × 180 mm

67 × 94 × 127 mm

1,6 kg

1,4 kg

Relay contacts in detail


Relay set

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