TELEPHONE No. AP 100
Subscriber’s amplifying set
This set is composed of a two-way amplifier and telephone instrument, both fitted in one cover. The exterior of the set is similar to that of the standard Ericsson. It is designed for use by persons with poor hearing and also for use with lines having low transmission properties. For this latter reason amplification of outgoing speech has also been provided for. The maximum amplification of incoming speech is about 2.3 neper (20 db) and this amplification can be regulated by means of a potentiometer, the knob of which is placed in the bottom right hand corner of the set. The input level should not, however, exceed about 1.3 neper (11.5 db), to avoid distortion. For outgoing speech the amplification is usually adjusted so that zero level is obtained at the near end of the line.
For lines giving poor transmission the output can be adjusted to a certain positive level by altering the tappings of a transformer. In this manner the amplification can be regulated 0.8 neper (7 db) in steps of 0.2 neper (1.75 db). The highest possible output level will consequently be + 0.8 neper (7 db). AP 100 is connected as an extension to an ordinary telephone instrument. Calls can then be carried on from the main instrument which is connected as usual, or from the amplifier, which is automatically connected when its handset is lifted. For calling, the main instrument must be used; this instrument also receives the incoming signals.
The set requires a battery RK 220 of 1.5 V and a battery RK 810 of 60 V; these two batteries may be fitted in a battery case RK 2312.
Taken from the L. M. Ericsson Telephones and Signalling Material Catalogue No. 188 (1934)
Last revised: September 30, 2019