SP300 SonarPhone T-Box Portable Installation Pack. 12V Portable Battery Pack to Take Your SonarPhone Anywhere!. The T-Box (SP300) options come in a portable system with a carry case to hold the battery and transducer cable. Your transducer is easily suction cup mounted on your boat. Easy to install on any boat, the skimmer style transdcuer and suction cup bracket can be used safely at speeds of 15 miles per hour. A safety cord is also supplied.. The SP300 comes with a 12V, 4.5 amp hour rechargea