In-series resistor mid-way in a battery stack: why?

[echelon]

I'm in the process of repairing a complex toy telephone, which is headed for being 25 years old.

I'm intrigued by the fact that the two pairs of AA/HP7 batteries are mid-point linked by a resistor, and not the conventional expectation of a shorting-strap to place the cells in series.

I've never seen this before, on any battery-portable equipment that I've repaired in my half-century of experience.

Any theories as to the design rationale?

[russell_w_b]

Originally Posted by echelon

Any theories as to the design rationale?

Wouldn't be some sort of crude transmission bridge, would it? Battery supply across both lines and speech 'encouraged' to go direct from 'phone to 'phone rather than be shunted by the battery?

This is a job normally done by a relay or inductor, but a resistor is cheaper.

Just a thought...

[Nicklyons2]

I'm thinking the same; it would allow simple hadsets with the earpiece and mic ostensibly being in parallel across the 'line'. The varying resistance of the carbon mic (with speech) would cause the current to vary in sympathy and hence the voltage across the battery stack. The 'line' voltage is thus modulated by the speech and can be easily coupled via a blocking capacitor to the earpiece.

[Herald1360]

If it's that crude, why bother with a capacitor- just let the standing dc through the parallel connected earpiece coils provide the magnetic bias instead of a permanent magnet. Even cheaper!