Latching relays

A latching relay is a two-position electrically-actuated switch. It maintains either contact position indefinitely without power applied to the coil.  It is controlled by two momentary-acting switches or sensors, one that ‘sets’ the relay, and the other ‘resets’ the relay. The latching relay maintains its position after the actuating switch has been released, so it performs a basic memory function.

There are two kinds of latching relays:

One latching type has two opposing coils with an over-center spring or permanent magnet hold the contacts in position after the coil is de-energized. A pulse to one coil turns the relay on and a pulse to the opposite coil turns the relay off.

Another latching type has a remanent core that retains the contacts in the operating position by the remanent magnetism in the core. This type requires a current pulse of opposite polarity to release the contacts. A variation uses a permanent magnet that produces part of the force required to close the contact; the coil supplies sufficient force to move the contact open or closed by aiding or opposing the field of the permanent magnet.

Time Chart

A pulse to one coil turns the relay on and a pulse to the opposite coil turns the relay off.

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  310 relay – Latching, safety critical, 18 contacts

  The 310 is a latching relay with 2 stable magnetically latched states. When 1 coil is energized, the relay actuates from magnetically latched position 1 to 2. When the other coil is energized, the relay actuates back from magnetically latched position 2 to 1. Relays have 18 double break contacts (Form X & Y - per customer specification) in all N/O and N/C combinations. (more…)
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  407 relay – Latching, safety critical, 40 contacts

  The 407 is a latching relay with 2 stable magnetically latched states. When 1 coil is energized, the relay actuates from magnetically latched position 1 to 2. When the other coil is energized, the relay actuates back from magnetically latched position 2 to 1. (more…)
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  BD-U200N relay – Latching, plug-in 4 pole

  Plug-in bistable railway relay with three change-over contacts and one normally closed contact, for reliable switching of very low currents (1 mA @5 VDC) up to currents of 10A @ 110 VDC. The contacts remain in the last powered position. Bistable by means of a permanent magnet. The built-in magnetic arc blow-out ensures adequate DC breaking capacity, resulting in long contact life. The integrated contact separation prevents cross pollution of…
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  KCD-U200 relay – Latching , 2 pole

  Plug-in bistable railway relay with two change-over contacts. The contacts remain in the last powered position, the position is clearly visible, optional shown via a position indicator. Bistable by means of two coils and a mechanical rocker mechanism. The two separate coils are galvanically isolated. The contacts are weld-no-transfer contacts: they are mechanically forced in the same position. (more…)
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  KDN-U200N relay – Latching, 8 pole

  Plug-in bistable railway relay with eight change-over contacts, for reliable switching of very low currents (1 mA@5 VDC) up to currents of 10A @ 110VDC. The contacts remain in the last powered position, the position is clearly shown via a position indicator. Bistable by means of two coils and a mechanical rocker mechanism. The two separate coils are galvanically isolated. The built-in magnetic arc blow-out ensures adequate DC breaking capacity…
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  SB relay – Latching, 4/3 contacts

  The SB is a latching safety critical relay with 2 stable magnetically latched states. When 1 coil is energized, the relay actuates from magnetically latched position 1 to 2. When the other coil is energized, the relay actuates back from magnetically latched position 2 to 1. (more…)
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  SBG relay – Latching, 4/3 gold contacts

  The SBG is a latching safety critical relay with 2 stable magnetically latched states. When 1 coil is energized, the relay actuates from magnetically latched position 1 to 2. When the other coil is energized, the relay actuates back from magnetically latched position 2 to 1. (more…)
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  SC relay – Latching, 8 contacts

  The SC is a latching relay with 2 stable magnetically latched states. When 1 coil is energized, the relay actuates from magnetically latched position 1 to 2. When the other coil is energized, the relay actuates back from magnetically latched position 2 to 1. Relays have 8 double break contacts with different configurations. The plug-in design offers secure locking feature for maximum ease of maintenance (no wires need to be…
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  TFBBU 400 relay – Flip flop, 4 contacts

  The TFBBU 400 is a flip flop relay with 4 double make / double break C/O contacts (form Z). The transient pull-in mode or dropout delay is fully programmable with a dip switch and activates or deactivates the relay. The access to dip switch is available by removing time delay cover. This feature prohibits frivolous field time delay setting. Function can be also be factory set on order. The plug-in…