KEY AND LAMP UNIT No. 3A
This Key and lamp Unit is a "Non-Ratebook Item", which is used on the EXTEL network.

The unit consists of 6 keys (1000 type) and 6 lamps and is used to support the local broadcast network with the functionality to connect a secondary circuit in the event of the main circuit failure and also to indicate alarms.  It can also switch in a spare amplifier.

There are two types of Key and Lamp Unit No. 3A.  The older version contains two Jacks No. 84C within the unit, whereas the later ones has the two jacks located external to the unit.

Circuit diagram SA/SAW4241 refers.
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Last revised: August 11, 2025
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