Ericsson DIALOG - Page 19

frequencies is therefore small and the response curve has a good
basic level.
Over the highest range of transmitter frequencies, the holes are
closed, since there is not time for full pressure equalization
between the two chambers. The diaphragm then works against
a smaller volume. As a result, the combined stiffness in c reases
with the frequency and the mechanical resonance curve of the
oscillating system is displaced towards the higher frequencies.
Covering the holes with fabric discs attenuates sharp resonance
peaks and smoothes out the response curve.
Fig. 28 The transmitter in cross section and parts
18
A
small hole (20) has been made in the diaphragm to counteract
adverse static pressure with air pressure variations and to a
counteract disturbances from low frequency room noise.
To protect it against mechanical damage, the transmitter is
provided with a perforated lid (18). Ingress of humidity is
prevented by a polyutheran disc (17) fixed inside the lid. The
capsule design and the choice of materials ensures that the trans-
mitter maintains its good characteristics under tropical condi-
tions .
3. 7.2 Receiver
Fig. 29
The
receiver
The external shape of the receiver can be seen in fig. 29.
In theory the receiver's magnetic system is of the conventional
type , but by a careful choice of material and accurate optimal
magnetizing, a considerable increase in output level has been
achieved.
The receiver body is of phenolic plastic. (1)
The diaphragm (8) is made of a special ferro-cobalt vanadium
alloy which exhibits high reversal permeability with normal
p
I
'D
TCI Library www.telephonecollectors.info