MUMBAI: Bharti Airtel and Vodafone Idea reduced the ring duration for outgoing calls from their networks to 25 seconds from 35-40 seconds to match that of Reliance Jio Infocomm, intensifying the interconnect usage fee (IUC) battle between the older phone companies and the Mukesh Ambani-owned telco.Bharti Airtel has reduced ring duration across its network while Vodafone Idea has done it in some circles. In the past 24 hours, the ringer time for all outgoing calls from Bharti Airtel’s network to Jio and Vodafone Idea has been shortened to about 25 seconds, Bharti Airtel executives told ET. Vodafone Idea has done the same, said a person aware of the development.Bharti Airtel and Vodafone Idea have alleged that Jio had cut ring time to 20 seconds — subsequently increased to 25 seconds in some circles earlier this week — to elicit a return call from its rivals in a bid to manipulate the IUC regime. A shorter ring before disconnection may spur recipients to call back the number.IUC is paid by a carrier to the one on whose network a call terminates, generating revenue for the telco that receives more calls.Bharti Airtel and Vodafone Idea are net revenue gainers in this respect, while Jio is a net payer of IUC. A shorter ring, Bharti Airtel has said, means more missed calls. This, in turn, would lead to more return calls to Jio’s network, enabling the latter to reduce its IUC payouts to incumbent telcos, Airtel said. Jio rejected this reasoning, saying 15-20 seconds was a global norm. Jio says its network is being bombarded by missed calls from incumbent telcos because it offers free voice services.Bharti Airtel and Vodafone Idea are trying to combat Jio’s move and protect their IUC revenue, experts said. Bharti Airtel and Vodafone Idea did not respond to queries. In a recent letter to the Telecom Regulatory Authority of India (Trai), Bharti Airtel had warned that it would reduce ring time, which would inconvenience subscribers, unless the regulator directed Jio to increase its own ring time. Bharti Airtel had said that Jio’s reduction had also rendered features such as call forwarding and call announcements useless.At a meeting with Trai on September 6, most telcos — Bharti Airtel, Vodafone Idea, Bharat Sanchar Nigam Ltd. (BSNL) and Mahanagar Telephone Nigam Ltd (MTNL) — backed 30 seconds of minimum ring time in the interests of consumers and network performance. Bharti Airtel pointed out at the meeting that Jio’s move had led to a change in voice traffic flow, with more calls now terminating on the latest telecom entrant’s network.“Before the change, the traffic pattern for Airtel vis-à-vis Jio was 65-35, incoming to outgoing calls,” a company representative said. “But within 48 hours, it changed to 60:40, and if unchecked, this could artificially change the pattern dramatically".Jio wanted ring time set at 25 seconds, saying 20 seconds was sufficient for a called party to respond, and that any longer wasted spectrum resources. It accused India’s older telcos of gaming the IUC regime, alleging that an outgoing call for the lowest class of 2G users for Bharti Airtel and Vodafone Idea costs as much as Rs 1.50 a minute. To avoid this cost, Jio argued, the subscribers of Bharti Airtel and Vodafone Idea and others give missed calls to Jio’s users to elicit a return call. This return call terminates on the incumbents’ networks, generating IUC revenue for them.Trai has since issued a discussion paper, ‘Duration of alert for the called party’, seeking views on maximum ring time to optimally use network resources. It has also reportedly asked telcos to arrive at a consensus on the matter before the consultation process concludes.