The Auto-Kall AK-400 is a DTMF controller with four 1-amp relays providing Normally Open outputs. The AK-400 is designed to directly interface with Maxon and Midland data radios. The DB-9 (DE9S) radio interface will plug directly into models SD-125, SD-225 and Headline HLD-100 radios, but it can be interfaced into most any radio. A separate PTT relay is provided to key the radio for transpond signals when a relay is activated. The transpond feature can be turned on and off. All programming is accomplished via a serial port using a common terminal program such as HyperTerminal. LED's are provided for Power, PTT and the four relays. Each relay has two codes that can be assigned to it for triggering it momentarily, latching or unlatching. The momentary function allows each relay to be programmed for a time period of 1 to 255 seconds. A separate audio jack is provided for directly connecting to a DTMF generator for testing. Most sound editing programs have a DTMF generation feature and the AK-400 can be plugged directly into a PC's audio output via the 3.5mm audio jack for testing. DTMF response up to 40ms tone / 20ms.