The WTX-4100 Series are our NEW Advanced Technology, Heavy Duty/Waterproof Speaker Microphones that feature WIRELESS PTT (Push-to-Talk) Capability. All WTX-4100 KITS now INCLUDE the compact PTT-4100W Transmitter unit to remotely activate the internal Wireless PTT receiver. The WTX-4100 series also features a special 3.5mm jack (threaded to keep out water) for use of external accessories such as earphones, headsets and throat mics.