RELAY-SWITCH No. 3106 N.L. 1-15
|Introduced soon after 1938 these relay-switches
are made of iron with two interlocking covers. The purpose of this
relay-switch is to isolate low voltage telephony circuits from mains
The units consist of a 3000 type relay, rectifiers and up to two 15amp mercury switches (Tubes, Mercury. No. 1) of the make variety. Where only one mercury tube is fitted, a Tube, Mercury, No. 1, Dummy is fitted in the spare position. Each relay has a standard C/O contact (pt) fitted.
The rectifiers are wired when required. They are generally used when the relay is operated from a low voltage AC source.
Now days this can all be done with discrete components - click here for more information.
The title number is interpreted as follows:-
Name - Type number - locking (L) or non-locking (NL) - quantity and
rating of mercury tubes
Referring to the title at the top of the page - this describes a relay-switch with a relay of the 3100 type, which is non-locking and includes one tube, mercury of 15amp and the unit fitted with a AW cover.
The No. 3106 is fitted with a Relay, No 4309.
When the relay is de-energised the spring in the upper compartment
assists in restoring the swinging arm back to it's home position.
Last revised: November 20, 2021