Montgomery County police will begin using a recorded message this summer to answer 911 emergency calls when all lines are busy, county officials said yesterday.

The disclosure comes less than a week after protests over the District police department's installation of a recording device forced it to temporarily disconnect the tape.

The message in Montgomery County will inform callers that they have reached the emergency line and that their calls will be answered in turn, said Maj. Robert Renfrew, chief of the police department's management services bureau.

"The tape will be a good, effective way to tell the public that their call has come through," Renfrew said. "We haven't really gotten any bad response, and I think people will understand it is just in an extreme situation when our system is overwhelmed."

Police officials, who explained the recording is part of changes begun in the 911 system last June, said they had no statistics on how long the average caller has to wait to get through to a dispatcher.

David Waas, communications systems engineer for the county, said that the recording is "not expected to be put in place before July 1." The tape is a feature of the Automatic Call Distribution system, a computerized system that Waas said will gather such information as the number of calls coming into the 911 line, the time each dispatcher spends on the telephone with a caller, and the number of calls coming in while all dispatchers are busy.

Capt. Ray Mulhall, spokesman for the county's fire and rescue services, said the recording would "aid the people, but I think we should first look at whether these things are manned correctly."

Mulhall said that 15 dispatchers answer the approximately 1,000 calls that come in to the 911 center each day.