State-owned Mahanagar Telecom Nigam Ltd has launched three additional basic plans for its Intregated Subscriber Digital Network or ISDN customers effective January 1.

The company would levy a monthly rental of Rs 500 under its 'General' plan and the calls would be billed at Rs 1.10 per unit with a 90 second pulse rate, MTNL officials said in Mumbai on Friday.

There would be no free calls under the General plan, they said.

Under the 'Special' plan, MTNL would charge a monthly rental of Rs 1,500 with 1,200 free calls and under the 'Super' scheme the rental would be around Rs 3,300 with 3,600 free calls, they said.

The unit call charges would be Rs 1.10 per unit under 'Special' plan and Re 1 for the 'Super' plan, the officials said.