No, ESU = emergency service unit are on duty all the time and drive utility type trucks with all sorts of equipment. they respond to odd calls requiring equipment patrol does not have...i.e. ....dog snares, entry equip, extrication equip and so forth. they are tactical and can hold down a critical scene until ERT = emergency response team arrives. you will always hear ESU and all frequencies. unit #s in the 80's...most of the time "ESU 85". ERT has alot of unmarked trucks but the marked one you will hear and see is "82"...both units are run under the same unbrella so you may hear they say ESU 82 or ERT 82 .... if you would like to see the trucks they drive go to FDNYtrucks.com and find newark police under "other states" then "essex county" also take a look at jersey city police in hudson county...they have alot of the same trucks but the jersey city page has more pictures.