Does it have the ALC input? What does Elecraft call it?This is explained in the FAQ on the Elecraft website:
What is the accessory connector used for?
The K3 has a rich set of I/O connections. In addition to the usual key jack, paddle jack, etc., there is a 15-pin D-series connector. It includes: band data, two configurable 5V logic inputs (e.g., for FSK) and two configurable 5V logic outputs, remote power switch input, PTT, key and auxbus (e.g., for a KRC2 or transverter). While this connector looks like a VGA video connector, it is not. The K3 does not provide any sort of video output. You can get a clear idea of the rest of the K3 I/O by looking at the rear panel drawing located on the back side (where else?) of the K3 data sheet.
What is the pin-out for the DE-15 Accessory connector?
1 - DIG0 FSK? software definable TTL digital input (5V MAX!)
2 - AUXBUS
3 - BAND 1 Output (TTL)
4 - PTT input (in parallel with MIC jack PTT )
5 - COMMON (via 100 uH choke)
6 - DIG Out 0 (software definable TTL digital output)
7 - DIG1 Input software definable TTL digital input (5V MAX!)
8 - POWER (pull to ground with open collector or switch to turn K3 ON)
9 - BAND 2 Output (TTL)
10 - KEY-OUT (Same purpose as KEY-OUT on rear panel but lower current rating. Suitable for accessories such as sequencers.)
11 - DIG Out 1 (software definable TTL digital output)
12 - COMMON (via 100 uH choke)
13 - BAND 0 Output (TTL)
14 - BAND 3 Output (TTL)
15 - ALC input (0 to +5V MAX)
vy 73 de toby
DD5FZ, 4N6FZ (ex dj7mgq, dg5mgq, dd5fz)
K2 #885, K2/100 #3248
K3/100 #??? (< #200)
DOK C12, BCC, DL-QRP-AG