CBS Entertainment yesterday announced April tryouts for two new series, the return of three series to the air and the switch of two current programs . . .

Taking at least a temporary rest will be "Twilight Zone," "Mary," "Foley Square" and the Saturday night movie . . .

"Bridges to Cross," starring Suzanne Pleshette as a Washington reporter for a news magazine, will debut Thursday, April 24, at 10 p.m. The next Thursday it will air in its regular 9 p.m. Thursday time slot . . . replacing "Simon & Simon," who move to 8 p.m., starting April 24 . . .

"Leo and Liz in Beverly Hills," a sitcom starring Harvey Korman and Valerie Perrine as a New Jersey couple trying to survive in California, will premiere Friday, April 25, at 8:30 . . .

"Charlie & Co.," starring Flip Wilson and Gladys Knight, returns to the 8 p.m. Friday time slot that same night. The two sitcoms replace "Twilight Zone" . . .

In addition, "Mickey Spillane's Mike Hammer" will be seen in repeats for three weeks in the 9 p.m. Tuesday time slot starting April 22 . . . replacing "Mary" and "Foley Square" . . .

"Airwolf" returns to the 9 p.m. Saturday slot on May 3, also with repeats . . .

"Magnum, P.I." moves into the 10 p.m. Saturday slot in repeats on May 3, following a two-hour broadcast on April 26 starting at 9 . . . Together, "Airwolf" and "Magnum" replace the Saturday movie . . .

We understand NBC News has been shopping Linda Ellerbee around among the network's five owned TV stations . . . and that Channel 4 has already taken a pass . . .

Ellerbee, whose duties are confined now to the "TGIF" Friday segment on the "Today" show, reportedly has written a fun book about her experiences in television . . .

Her contract is up soon with NBC News and it's known that "Today" would like to retain her . . . but whether that's enough to keep her busy may be the problem . . .

Speaking of "Today," Channel 4's very own Lea Thompson will be one of several people due to sit in for coanchor Jane Pauley when she goes on maternity leave in July . . .

Locally, there's increased talk around town of a couple of pending on-air changes at Channel 7, maybe by next week . . .

NBC Chairman Grant Tinker yesterday responded to CBS Inc. Chairman Tom Wyman's charge on Tuesday that an "NBC Nightly News" segment about his Records group president represented "a second-class example of broadcast journalism" . . .

"Tom Wyman's comments were unfortunate and his words ill-chosen. NBC News does not do second-class work," said Tinker . . .

Later in the day, a spokesman for Wyman said the CBS chairman would have no comment on the NBC chairman's comment . . .

Wyman took exception to a report Monday on "Nightly News" about federal inquiries into the record business that included references to CBS Records and its president, Walter Yetnikoff . . . as well as to the "implication and innuendo" of a suggestion in the broadcast "that the industry as a whole had been involved in unethical and/or illegal conduct and that, in particular, the leadership of the industry was implied to be knowledgeable and perhaps even involved" . . .

Wyman also said in a Tuesday memo that "we are exploring whether further steps can be taken to correct the extreme misimpressions created by this broadcast" . . .

Again yesterday, a spokesman for Yetnikoff declined to speculate what, if any, those "steps" against NBC might be . . .

NBC News President Larry Grossman will be in Washington Monday to take a good hard look at the latest pilot of "American Almanac," which was originally set for screening earlier this week in New York but went back to the shop for a tune-up at the NBC News bureau here . . .

The magazine's format, even the opening and the set, is still being -- you should forgive the expression -- tinkered with . . . but it's getting closer and closer to that promised June launch date, TV Column fans . . .

The Rev. M.G. (Pat) Robertson, founder of the Christian Broadcasting Network in Virginia Beach, has announced that due to a reduction in contributions, CBN has been forced to sell three TV stations, lay off at least 42 employes and cancel CBN's toll-free telephone number . . .

On the block will be WYAH in Portsmouth, Va., WXNE in Boston and KXTX in Dallas . . .

After grumbling about it the past few weeks, NBC has decided that it will, after all, broadcast the 13th annual Daytime Emmy Awards sometime in mid-July . . .

Last year, the three networks decided to renew the daytime award telecasts as long as the New York-based National Academy of Television Arts & Sciences let the more proficient -- in their view, anyway -- West Coast-based Academy of Television Arts & Sciences take effective control . . .

CBS kicked off the three-network rotation last year but NBC initially balked at a two-hour broadcast this year, since the Daytime Emmys cut regular daytime revenue . . .

After the two sponsoring academies agreed to a 90-minute telecast, NBC, in the spirit of industry good fellowship, went ahead . . . Also in the News

The Corporation for Public Broadcasting announced yesterday that for the eighth straight year, a Fourth of July concert featuring the National Symphony will be broadcast from the west lawn of the U.S. Capitol . . .

Henry Mancini will conduct, and pianist Andre Watts and vocalist Sarah Vaughan will perform. E.G. Marshall will host . . .

NBC Entertainment announced yesterday that "Hill Street Blues" will be back for a seventh season this fall. Just to make it official, John Litvack, vice president, Current Dramatic Programs, appeared on the air last night at the conclusion of the last regular "Hill Street" episode of this season to say:

"Hi, I'm John Litvack, the NBC executive on 'Hill Street Blues.' Every year at the Emmys, 'Hill Street' has come away a big winner, and every year I never get thanks. But that's okay, because tonight I get the chance to thank you -- the loyal 'Hill Street' watchers -- and the cast and producers by announcing the show's renewal for next season. Meow" . . .

Writing before the fact, it would appear that Litvack's "meow" will precede the regular "meow" in the MTM Productions logo at the conclusion of the program, making last night's "Hill Street" a two-meow episode . . .

Along the Ratingzzz Rialto: "Today" finished first again the morning network race, with a 5.8 Nielsen rating and a 23 percent audience share for the week ending March 28 . . .

"Good Morning America" was close with a 5.7/23 while "CBS Morning News" (what else is News?) finished in the cellar for the 117th straight week with a 3.3/14 . . .

Oh, by the way. A comparison of 1985 with 1986 first quarter (January-through-March) figures shows first-place "CBS Evening News With Dan Rather" on a slide . . . and both "NBC Nightly News With Tom Brokaw" and "ABC World News Tonight With Peter Jennings" sneaking up . . .

Based on Nielsen ratings:

CBS' average audience so far in 1986 is 11.7 million TV homes, down from 12.1 million in 1985; NBC averages 10.9 million, up from 10.1 million; and ABC jumps to 10.4 million from 9.7 million . . .

In 1985 CBS enjoyed a 2.4-million-home advantage over third-place ABC on an average evening. That margin has "shrunk" to 1.3 million so far this year . . .

Total average network news audiences are up about 1.2 million TV homes, to 33.1 million, since the same period last year . . .

Work begins next week on the first of three "Love Boat" specials slated for next season on ABC, which is all "Love Boat" fans are going to get as Captain Smiley Stubing and the gang sail straight for the Great Ratings Reef . . .

In the cast: Tony Franciosa and Gina Lollobrigida, working together for the first time since their magic 1961 MGM film, "Go Naked in the World" . . .

Susan Lucci, who plays Erica Kane on ABC's "All My Children," has signed for another two years . . .