MÄRKLIN H0 conventional driving and electromechanical automatisation

 

 

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Märklin-H0-Knowledge

Circuits for advanced users – Automation of Processes

The relatives of the Märklin universal remote switches

 

 

state: 13.02.2026 12:12

 

 

 

It is important in many circuits:

the universal remote switch - that's what Märklin calls this bistable relay.

A relay is an electrically operated switch that is switched over by one or two electric solenoids.

There are two operating principles:

o        Monostable: one coil activates the switch and a spring resets it when the control voltage is removed.

o        Bistable: one coil activates the switch and a second coil resets it. Both positions are stable thanks to mechanical measures and, depending on the design, may also be resistant to vibrations.

 

Why is a bistable relay important?

Sometimes you want to fix a switching state on your model railway layout for a longer period of time – just as turnouts and signals remain in their position when you pull the power plug.

Bistable relays used to be similar in design to turnout and signal drives. Today, there are also electronic means of maintaining a switching state permanently without a power supply.

Märklin is, of course, not the only manufacturer that builds (or built) such devices.

In this article, I present a number of alternative bistable relays, some with special features.

If you know of any other products, please let me know.

 

Common features

As a rule, bistable relays have two solenoids that pull an armature back and forth, thus realizing two switching positions.

Note:
The relay should be mounted – on a base, on a wall, under a plate – so that the armature is HORIZONTAL. This prevents the weight of the armature from influencing the switching behavior.

The connection is therefore usually made with an AC power supply from the transformer connection “L” and two control lines for the two switching positions, which are briefly (!) supplied with a voltage pulse from the transformer connection “0”.

The relays are equipped with different working contacts.

Some relays have an integrated limit switch. This means that the duration of the control signal is irrelevant for them.

 

An overview

 

 

Manufacturer

Number

Contacts
(CO = changeover
NC = normal closed
NO = normal open)

Connections

Special feature

 

 

Märklin
(2nd hand)

7045

1x CO

model railway connector

 

 

 

Märklin
(2nd hand)

7245

1x CO + 2x NC/NO

plugs and terminals

 

 

 

Märklin
(new)

7244

4x CO

terminals

continuous voltage resistant

 

 

Faller
(2nd hand)

649

2x NC/NO

plugs

 

 

 

Eheim
(2nd hand)

TRV

2x NC/NO
or 2x NC + 2x NO

plugs

two functional variants

 

 

Trix Express
(2nd hand)

6590

1x CO

terminals

 

 

 

Trix Express
(2nd hand)

6591

4x CO

terminals

 

 

 

Trix Express
(2nd hand)

6592

2x CO

terminals

end switch

 

 

BTTB/Tillig
(2nd hand)

8410

2x CO

terminals

 

 

 

Piko
(2nd hand)

---

1x CO

terminals

end switch

 

 

Fleiscmann
(2nd hand)

6956

2x CO

terminals

 

 

 

Roco
(new)

10019

4x CO

spec. plugs /
soldering

end switch

 

 

Viessmann
(new)

5551

4x CO

plugs

 

 

 

Viessmann
(new)

5552

2x 2 CO

plugs

two relays in one housing

 

 

Hongfa
(new)

HFD2 … L2

2x CO

soldering

continuous voltage resistant (?)

 

 

 

The “universal remote switches” from Märklin.

Märklin designed signals without displays in parallel with the signal types.

UFS 7045 looked like the drive units of the 70xx series signals, double solenoid coil.

UFS 7245 looked like the drive units of the 72xx series signals, double solenoid coil.

UFS 7244 is a fully electronic development independent of other products.

 

 

Märklin 7045 is no longer manufactured and is only available second-hand.

Märklin 7045 has 6 connections:
4 wires and 2 unlabeled sockets.

Märklin 7045 has a changeover switch.

Connection and function:

The yellow wire to “L” on the transformer (16V AC),

the blue wires with red and green plugs can be connected briefly (!) to ground “0” on the transformer to activate the coils, NO limit switch,

the red wire is connected alternately to one of the sockets.

Märklin 7045 has a manual switch lever.

 

   

 

 

 

Märklin 7245 is no longer manufactured and is only available second-hand.

Märklin 7245 has 10 connections:
3 wires and 7 labeled terminals.

Märklin 7245 has 1 changeover switch/selector switch and 2 normally open/normally closed contacts.

Connection and function:

The yellow wire to “L” of the transformer (16V AC),

the blue wires with red and green plugs, optionally activated briefly (!) to ground “0” of the transformer, activated the coils, NO limit switch.

Changeover/switch from terminal 2 to terminals 1 or 3,

normally open/normally closed between terminals 4 and 5
and between terminals 6 and 7.

Märklin 7245 has a manual switch lever.

This relay is known to be unreliable.

 

   

 

 

 

 

 

Märklin 7244 has 15 connections:
3 wires and 12 labeled terminals.

Märklin 7244 has 4 changeover switches/switches.

Connection and function:

The yellow wire connected to “L” on the transformer (16V AC),

the blue wires with red and green plugs, optionally also for longer periods (!) to ground “0” of the transformer, activate the switchover.

Changeover/switch from terminal 2 to terminals 1 or 3,
of which there are 4 sets.

Märklin 7244 has no manual control option.

 

   

 

 

The Faller No. 649 switching relay

Two powerful coils work inside this relay.

The armature is centered in each coil and connects two contact springs with its pin-shaped ends.

 

 

Faller 649 is no longer manufactured and is only available second-hand.

Faller 649 has 7 connections: 7 labeled sockets.

Faller 649 has 2 NO/NC contacts.

Connection and function:

Yellow socket “0” to “L” of the transformer (16V AC),

blue sockets “x” and ‘y’ optionally activate the switchover briefly (!) to ground “0” of the transformer, NO limit switch.

Pulse at socket “x” disconnects the red sockets ‘3’ and “4”
and connects the green sockets “1” and “2”,

pulse at socket “y” disconnects the green sockets ‘1’ and “2”
and connects the red sockets “3” and “4”.

Faller 649 has no manual control option.

 

    

    

 

 

The EHEIM TRV switching relay

This relay was originally designed to control the EHEIM overhead bus (trolleybus). The accompanying instructions describe only such applications.

The armature is designed as a finger that is mounted on a pivot point and is alternately attracted by the two coils.

The finger connects two pairs of contact springs in each switching position.

The EHEIM TRV is no longer manufactured and is only available second-hand.

The Eheim TRV has 8 connections:
7 labeled sockets and one contact on a mounting hole.

There are 2 ways to connect the Eheim TRV.
This results in two different circuit diagrams.

The EHEIM TRV does not have a manual control option.

 

 

Variant 1:

Connection exclusively to the sockets:

In this connection type, the EHEIM TRV has 1 normally closed contact and 1 normally open contact.

Connection and function:

Socket “0” to “L” of the transformer (16V AC),

sockets “1” and ‘2’ optionally activate the switchover briefly(!) to ground “0” of the transformer, NO limit switch.

Pulse at socket “1” disconnects sockets ‘3’ and “4”
and connects sockets “5” and “6”,

Pulse at socket “2” disconnects sockets ‘5’ and “6”
and connects sockets “3” and “4”.

 

Variant 2:

Connection to the sockets and to the contact on the mounting hole:

In this connection type, the EHEIM TRV has 2 normally closed contacts and 2 normally open contacts with a common input.

Connection and function:

Socket “0” to “L” of the transformer (16V AC),

Sockets “1” and ‘2’ optionally briefly(!) to ground “0” of the transformer
activate the switchover, NO limit switch.

Connection “M” to input signal.

Pulse at socket “1” disconnects sockets “3” and “4” from ‘M’
and connects sockets “5” and “6” to “M”,

Pulse at socket “2” disconnects sockets “1” and “2” from ‘M’
and connects sockets “3” and “4” to “M”.

 

 

    

 

 

The TRIX-EXPRESS relays

The TRIX-EXPRESS relays are no longer manufactured and are only available second-hand.

There were three versions of a bistable relay:

No. 6590 with one changeover/changeover switch and WITHOUT limit switch,
No. 6591 with four changeover contacts/changeover switches and WITHOUT limit switch, and
No. 6592 with two changeover contacts/changeover switches and WITH limit switch.

ATTENTION: Officially, the coils are designed for 14V AC!

The housings were available in gray and transparent.

 

 

The TRIX-EXPRESS 6590 has 6 labeled connection terminals.

The TRIX-EXPRESS 6590 has 1 changeover switch/selector switch.

Connection and function:

Terminal “0” to “L” of the transformer with voltage reduction to 14V AC,

terminals “1” and ‘2’ optionally briefly(!) to ground “0” of the transformer
activate the switchover, NO limit switch.

Pulse at terminal “1” switches terminal A0 to terminal A1,

pulse at terminal “2” switches terminal A0 to terminal A2.

The TRIX-EXPRESS 6590 has a manual switch lever.

 

 

 

 

 

The TRIX-EXPRESS 6591 has 15 labeled connection terminals.

The TRIX-EXPRESS 6591 has 4 changeover/switching contacts.

Connection and function:

Terminal “0” to “L” of the transformer with voltage reduction to 14V AC,

Terminals “1” and ‘2’ optionally briefly(!) to ground “0” of the transformer
activate the switchover, NO limit switch.

Pulse at terminal “1” switches   terminal A0 to terminal A1,
                                terminal B0 to terminal B1,
                                terminal C0 to terminal C1 and
                                terminal D0 to terminal D1,

pulse at terminal “2” switches   terminal A0 to terminal A2,
                                terminal B0 to terminal B2,
                                terminal C0 to terminal C2 and
                                terminal D0 to terminal D2.

The TRIX-EXPRESS 6591 has a manual switch lever.

 

 

 

 

 

The TRIX-EXPRESS 6592 has 9 labeled connection terminals.

The TRIX-EXPRESS 6592 has 2 changeover switches/switches.

Connection and function:

Terminal “0” to “L” of the transformer with voltage reduction to 14V AC,

Terminals “1” and “2” optionally connected to ground “0” of the transformer – also for longer periods (!) – activate the switchover.

After switchover, the relay automatically removes the voltage from the coil; WITH end switch!

Pulse at terminal “1” switches   terminal A0 to terminal A1,
                                terminal B0 to terminal B1,

Pulse at terminal “2” switches   terminal A0 to terminal A2,
                                terminal B0 to terminal B2.

The TRIX-EXPRESS 6592 has a manual switch lever.

 

  

 

 

The 8410 switching relay from Berliner TT Bahnen or Tillig

 

 

The 8410 switching relay is probably no longer manufactured and can only be obtained second-hand.

The 8410 switching relay has 9 labeled connection terminals.

The 8410 switching relay has 2 changeover/changeover switches.

Connection and function:

Terminal “R” to “L” of the transformer (16V AC),

Terminals “1” and “2” optionally activate the switchover briefly (!) to ground “0” of the transformer, NO end switch.

Pulse at terminal “1” switches   terminal A to terminal A1,
                                terminal B to terminal B1,

Pulse at terminal “2” switches   terminal A to terminal A2,
                                terminal B to terminal B2.

The 8410 switching relay has a manual switch lever.

 

    

 

 

The PIKO relay

 

 

The PIKO relay is no longer manufactured and is only available second-hand.

The PIKO relay has 8 connection terminals without labeling.

The numbers in the circuit diagram correspond to the following diagram:

The PIKO relay has 1 changeover contact/changeover switch.

Connection and function:

Terminal 3 to “L” of the transformer (16V AC),

terminals 1 and 2 optionally – even for longer periods (!) – to ground “0” of the transformer activate the changeover; WITH end switch.

A position signal can be tapped at terminals 4 and 5.

A pulse at terminal 1 switches  terminal 8 to terminal 6 and
                                terminal 3 to terminal 4 and
interrupts the connection from terminal 3 to the coil and terminal 5.

A pulse at terminal 2 switches  terminal 8 to terminal 7 and
                                terminal 3 to terminal 5 and
interrupts the connection from terminal 3 to the coil and terminal 4.

The PIKO relay has a manual switch lever.

 

    

 

 

 

Fleischmann Universal Relay 6956

I do not own this relay, so the information provided is only speculation based on its external appearance.

 

 

The Fleischmann Universal Relay 6956 is no longer manufactured and is only available second-hand.

The Fleischmann Universal Relay 6956 has 9 labeled connection terminals.

The Fleischmann Universal Relay 6956 apparently has 2 changeover contacts/switches.

Connection and function:

Presumably terminal “B” to “L” of the transformer with voltage reduction to 12 to 14V AC (presumably AC, because that is/was generally customary),

presumably terminals “A” and ‘C’ selectively activate the switchover, probably briefly(!), to ground “0” of the transformer,
presumably NO end switch.

A pulse at terminal “A” or alternatively “C” presumably switches terminal 2 to terminal 1 or 3 and terminal 5 to terminal 4 or 6.

The Fleischmann 6956 relay has two manual switch buttons.

vermutlicher Schaltplan

 

 

 

 

Roco changeover relay 10019

 

 

The Roco changeover relay has 5 connection tongues, each with 3 contact surfaces, i.e. 15 connections, without labeling.

Roco offers the 3-pin connector 10603 for connecting 3 wires each = connection of a switch. However, you can also solder to the contact surfaces.

The numbers in the circuit diagram correspond to the following drawing, view of the top side with the circuit diagram:

The Roco changeover relay has 4 changeover contacts/switches.

Connection and function:

Contact surface “X0” to “L” of the transformer (16V AC),

contact surfaces “X1” and ‘X2’ optionally – even for longer periods (!) – to ground “0” of the transformer activate the changeover; WITH end switch.

Pulse at  contact surface “X1” switches
         contact surface “A0” to contact surface “A1” and
         contact surface “B0” to contact surface “B1” and
         contact surface “C0” to contact surface “C1” and
         contact surface “D0” to contact surface “D1” and
interrupts the connection from contact surface “X1” to the coil.

Pulse at  contact surface “X2” switches
         contact surface “A0” to contact surface “A2” and
         contact surface “B0” to contact surface “B2” and
         contact surface “C0” to contact surface “C2” and
         contact surface “D0” to contact surface “D2” and
interrupts the connection from contact surface “X2” to the coil.

The Roco changeover relay has a manual switch lever.

 

      

    

 

 

Viessmann universal relay

I do not own this relay, so the information is only speculation based on its external appearance.

 

 

The Viessmann universal relay 5551 has 15 connection sockets without labeling.

The Viessmann universal relay 5551 has 4 changeover contacts/switches.

The numbers in the circuit diagram correspond to the following illustration, view of the top side with the circuit diagram:

Connection and function:

Socket “0” to “L” of the transformer with 16V AC,

Sockets “1” and ‘2’ optionally activate the switchover briefly (!) to ground “0” of the transformer, NO limit switch.

Pulse at socket “1” switches socket A0 to socket A1, socket B0 to socket B1, socket C0 to socket C1, and socket D0 to socket D1.

pulse at socket “2” switches socket A0 to socket A2, socket B0 to socket B2, socket C0 to socket C2, and socket D0 to socket D2.

The Viessmann universal relay 5551 has a manual switch lever.

 

 

 

 

 

The Viessmann universal relay 5552 has 18 connection sockets without labeling.

The Viessmann universal relay 5552 contains 2 relays, each with 2 changeover contacts/switches.

The numbers in the circuit diagram correspond to the following illustration, view of the top side with the circuit diagram:

Connection and function:

Sockets “AB0” and ‘CD0’ connected to “L” of the transformer with 16V AC,

Sockets “AB1” and “AB2” or “CD1” and ‘CD2’ optionally activated briefly(!) to ground “0” of the transformer activate the switchover, NO limit switch.

Pulse at socket “AB1” switches socket A0 to socket A1, socket B0 to socket B1,

Pulse at socket “AB2” switches socket A0 to socket A2, socket B0 to socket B2.

A pulse at socket “CD1” switches socket C0 to socket C1, socket D0 to socket D1.

A pulse at socket “CD2” switches socket C0 to socket C2, socket D0 to socket D2.

The Viessmann universal relay 5552 apparently has no manual override.

 

 

HongFa HFD2 … L2 Printed Circuit Relay

These relays are designed for printed circuit board mounting. They have solder tabs with a 2.54 mm pitch.

The type we need has two pairs of connection tabs for actuation, i.e., one pair of connections for switching to position I and one pair of connections for switching to position II.

There are types for 12V DC and also for 5V DC and 24V DC, which means that DC voltage is required with a different voltage than that supplied by the Märklin transformers at the “L” connection. One option would be to use an old Märklin speed controller set to 12 V, for example, and connect a rectifier to “B” and “0”. Alternatively, a speed controller from the DC world could be used, or a new power supply unit from an electronics retailer.

The big advantage of these relays is that they are much cheaper than electromechanical ones. However, you need to be able to solder to connect them to the wires. With circuit board material and connection terminals, the price advantage is soon lost.

However, complex control systems become small and inexpensive.

 

 

The HongFa HFD2 has 10 solder tabs in a 2.54 mm = 1/10 inch grid.

The HongFa HFD2 has 2 changeover switches/selectors.

The HongFa HFD2 is available for 12V DC and 5V DC operating voltage.

Connection and function:

Connections 15 and 16 to the negative terminal of the DC transformer.

A connection 1 and 2 optionally to the positive terminal of the transformer – also for longer periods – activates the switchover.

A pulse at connection 1 switches
connection 6 to connection 4 and
connection 11 to connection 13.

A pulse at connection 2 switches
connection 6 to connection 8 and
connection 11 to connection 9.

 

 

 

 

 

 

There are other print relays on the market.

 

 

 

 

 

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