Intercommunication table telephone
These telephones operate with battery ringing. To make a call it is only necessary to turn the switch to the de sired number and press the button. If the called number is disengaged, the bells of both the calling and the called instrument will ring. If on the other hand it is engaged, neither bell will be actuated, unless the system is connected for single line working; in the latter case both bells will ring. An in coming call will ring the bell independent of the position of the switch. When the microtelephone is lifted, the telephone is immediately connected to the calling line independent of the position of the switch. The conversations are non-secret and several conversations can be carried on at a time.
Each telephone requires a microphone battery, M. Batt., one consisting of 2 dry cells RK 210 being suitable.
One signalling battery is necessary for the whole plant. This should be located as near the centre of the system as possible. The number of dry cells required for this battery is determined by the size of the plant and by the length of the lines.
4 to 5 cells RK 210 will be necessary. A suitable battery case is RK 2300.
A suitable cable is Type EEB with a minimum of 22 and 42 conductors for 10 and 20 telephones respectively.
Suitable junction boxes are HM 160/10 and HM 160/20.
By means of brackets RK 5010 the telephones HA 270 may be mounted as wall sets.
The telephones can also be used for single line working.
For extension of existing systems having telephones HA 250, the new type HA 275 should be used. This telephone is similar in appearance to HA 270. Telephones HC 130 & HC 210 can be used as extensions.
microtelephone RE 1044 of black bakelite with removable capsule transmitter RC 4000/40, 40 ohm, and cord RS 6160, switch for selecting the lines, press button for calling, DC bell 100 ohm, case of black bakelite, terminal block, terminal block cord length 2 m.
height 140 mm, width 233 mm, depth 175 mm.
HA270/l0 - 10 circuits
HA270/20 - 20 circuits
Taken from the L. M. Ericsson Telephones and Signalling Material Catalogue No. 188 (1934)
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