Unlike mobile phones landline phones do not have batteries

The basic difference in the working of the land line telephone and the mobile phone is that while the former is of wired working, the later is of wireless working system.

In the wired working method, the land line telephone is connected to the local Telephone Exchange by means of two wires.

The battery energy required for the telephone is extended from the Telephone Exchange through these wires. Since the source of energy required for the entire telephones connected to the exchange is thus centralized, this type of working is known as Central Battery System.

It is noteworthy in this context that prior to the introduction of the C B System, Magneto Type Telephone Exchanges were in vogue, in which each telephone apparatus had a battery attached to it. Actually, the purpose of the battery is to energise the vital parts in the telephone, viz. transmitter and receiver.

In order to activate the bell in the telephone, this battery is not enough, and a separate ringing voltage is fed on the line from the exchange in the C B System.

In the Magneto System, the operator in the exchange had to manually rotate a hand generator to pass on the ringing current on the line. In the telephone set also, a hand generator was attached to ring up the exchange for making a call.

In the wireless system of mobile, distribution of battery from the exchange is not feasible, in the absence of any physical line. The signals containing speech etc. to and from the telephone handset are transmitted by frequencies over air, and for its generation and also reception, various tiny equipment in it have to be activated for which the required battery is provided in the set itself.