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GENERAL

The No 4 receiver was also known as the MR-4 (Marine Receiver No 4). It was designated for use by the British Merchant Marine.
It could consist of the following mixture of subassemblies:

Receiver Type 226
Long wave adaptor Type 229
Single note magnifier. Type 227
Note filter Type  282 .(optional)

Left module - Tuner; Middle module - Receiver; Right module- Note Amplifier. The note filter is not shown here. (Image courtesy  (Handbook of Technical Instruction)

DESIGNATORS FOR THE No. 4 RECEIVER

* No. 4A - If the receiver and long wave adapter only  are used,. this combination is called No. 4A
* No. 4B- The normal method of cornbining the above  units is to use the long wave adaptor, the receiver,
and the note magnifier as assembled in Fig 359 , this eornbination is known as Marine Receiver, No. 4B.
* No.4D  - When only the receiver is used, it is called No. 4D
*No. 4E  - When only the receiver and note amplifier are used, that's called No. 4E.
* No. 4F When the type 282 note filter is used with the receiver and note amplifier,  the  designation changes to No. 4F

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Contributors and Credits:

1) Lewis Bodkin  <05bodkin555(at)gmail.com>
2) Handbook of Technical Instruction for For Wireless Relegraphists
 

Sept 13/19