Breastplate Transmitter with Head Gear Receiver.
from 1897 LM Ericsson Catalog 4th edition

This arrangement will be found very convenient for busy central station work, where it is desirable for the operator to have both hands free. The transmitter can be turned, by which the mouthpiece may be adjusted to any suitable distance to the mouth. The mouthpiece is removable.

When the operators are very busy the primary key is replaced by a spring arranged so, that the current is connected when the mouthpiece is in the ordinary speaking position, but disconnected when the transmitter is turned back, the frame is thus completely insulated and does not as in the other, serve as conductor. The advantage of this arrangement is that it spears the battery.

The plate, transmitter and receiver are all made of aluminium, which somewhat reduces the weight.

STSF org