These magneto telephones are variants of the automatic Plan Telephone (BPO type 710). In general they offer the same attractive design features as the auto telephone, but with press-button generator signalling replacing the dial function.
Main Design Features
Table and wall instruments.
High-quality transmission and reception based on CCITT recommendations.
Transistor ringing-current generator.
High reliability, giving low maintenance requirement.
Stain-resistant high-impact shell mouldings.
Chromium-plated carrying handle fitted under handset (on table telephone).
Off-hook position for handset.
Tropical finish to withstand extreme climatic conditions
For use on exclusive and party lines.
Table and Wall
High-gloss, high-impact acrylonitrile butadiene styrene (ABS) copolymer moulding.
A press button for ringing is situated above the dummy dial
Lightweight, with screw-fitting mouthpiece and earpiece.
Replaceable receiver and transmitter insets.
Receiver BPO-type 4T (rocking-armature type).
Transmitter BPO-type 16 (carbon-granule type).
Toughened black polystyrene.
Two-piece. high-impact ABS copolymer moulding, housing four terminals.
PVC covered, copper-tinsel conductors in PVC sheath.
Spade terminals for easy connection to terminal blocks
Coiled handset cord extensible from 10 in (254mm) to 6 ft (1829mm).
Desk cord for table model is 6 ft (1829mm) standard: other lengths available for large-quantity orders.
Consists of a pre-tensioned springset with palladium contacts, protected overall by a Perspex cover requires no maintenance. Internal manually-operated spring-latch locks the cradle switch in the 'handset-on' position to allow reception of calls during instrument inspection.
Twin-coil type with double gongs. Coil resistance 5k ohms
Impedance to voice frequencies 10kohms
6V type with ringing frequency of 12-30Hz (dependent Wall telephone N2208H on load).
Output voltage 170V peak-to-peak (off load).
Current drain 170mA (off load) up to 1 A (dependent on load).
6V battery (4 x 1.5v cells), installed near the telephone, supplies the power for the generator and telephone transmission circuit.
Available in black, ivory and two-tone grey.
When supplied in the two-tone colour, the handset, terminal block and dial dummy are in the darker tone.
Overall Dimensions and Weight (approx.)
|Item||Height in. (mm)||Width in. (mm)||Depth in. (mm)||Weight lb.oz.(kg)|
|Table model||4.75 (121)||9.2 (238)||8.8 (226)||4lb 10oz (2.1)|
|Wall model||8.8 (226)||9.4 (238)||5.5 (140)||4lb 10oz (2.1)|
Ambient Temperature: 5' to 50'C.
Relative humidity Up to 100% (short-term use): up to 85% (continuous use).
To cater for certain party-line requirements an unwired capacitor is provided in the telephone for inclusion in the bell circuit. Full wiring instructions are given in the telephone circuit affixed to the inside of the cover.
If requested on order telephones can be supplied with the capacitor wired into circuit.
PUBLICATION No. 7643, 2/76
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