RECEIVER, INSETS

Used in most early Bakelite handsets. 80 ohms resistance.

Superseded by the Receiver Inset No. 2P.

Used with an Earpiece No. 18 and Diaphragm No. 12 (Stalloy - 32mm diameter).

Note the exposed coils in the centre of the receiver.

See picture below for Pole Grinding in the factory.

Used in later Bakelite handsets. 50 ohms resistance.

Used with an Earpiece No. 23 and Diaphragm No. 25 (Permandur - 32mm diameter).

Note the top of the receiver is enclosed, with a small air vent.

Receiver Inset No. 2P Mark 3 was introduced around 1949.

Siemens Brothers code - Receiver No. 53C

Used in 700 handsets.  Introduced as an aid to those who wore hearing aids.  The receiver had a coil of wire wound around the outside and this would interact with a hearing aid that was switched to the 'T' setting.

No. 1/3T was introduced in 1980.

Used in Headsets and Trimphones.

20 ohms resistance.

Used on Receiver, Head-gear No. 16.

600 ohms resistance.

Used in many 700 type telephones.  20 ohms resistance.

Later Receiver Insert No. 4's comprised of a No. 3T inserted into a plastic housing which resembled the No.4 - dimension wise.