diff --git a/README.md b/README.md
index e670a49..1853dbb 100644
--- a/README.md
+++ b/README.md
@@ -47,6 +47,7 @@ scorer: red for a dupe, green for a new multiplier, blue for points.
 | Contests | CQ WW (CW, SSB, RTTY), CQ WPX (CW, SSB, RTTY), WAE (CW, SSB, RTTY), ARRL DX, IARU HF, Sweepstakes, RTTY Roundup, NAQP, OK/OM DX (CW), YOTA, IOTA, EU DX Contest, CQ 160, ARRL 10M, REF, Ukrainian DX, Russian DX RTTY, RDAC, YO DX HF, Oceania DX, All Asian, SARTG RTTY, BARTG Sprint, Mexico RTTY, IARU Region 1 Field Day, general logging, and user-defined `.udc` contests |
 | Log | N1MM `.s3db`, Cabrillo 3.0 out, ADIF in and out |
 | While typing | dupe check, multiplier check, points, country and zone from the country file, exchange filled from a call history file |
+| While transmitting | a digital message is held in the transmit pane and fed to the engine a character at a time, so what has not gone out can still be rewritten; what has gone out is red, and the engine idles when it catches up with the cursor |
 | Windows | entry, log, check, bandmap, available mults and Qs, score summary, grey line, telnet, digital interface |
 | Editing | double-click a cell in the log, or open the whole contact with Ctrl+Y; Delete removes it. All of it goes out to the other stations |
 | Radio | one or two radios over hamlib `rigctld`, split, reconnecting on its own |
diff --git a/docs/unfinished.md b/docs/unfinished.md
index 2f950f8..11bcb8d 100644
--- a/docs/unfinished.md
+++ b/docs/unfinished.md
@@ -39,9 +39,19 @@ hardware TNCs — are not here either, though `DigitalEngine` is the place to ad
 them.
 
 The receive pane has been driven with a stand-in bridge that prints prepared
-text, which is how the printing, the colouring and the Letters/Figs box were
-checked. Nothing has been decoded from a real signal: this machine has no sound
-card.
+text, which is how the printing, the colouring, the Letters/Figs box and the
+type-ahead transmit pane were checked. Nothing has been decoded from a real
+signal and nothing has gone on the air: this machine has no sound card, and
+MMTTY does not start on it.
+
+**What paces the type-ahead pump.** It counts character times off the clock at
+the baud rate in the digital settings, so it runs a little behind the engine
+rather than ahead of it. The engine can be asked instead: `XMMT.ocx` has a
+`TxBufLen` property, and a probe against the control shows it answers, though
+what it answers while a message is going out could not be measured here because
+the engine will not start. Reporting it from the bridge would make the red text
+exact and let the pump keep the engine's buffer full rather than leaving a gap
+between characters.
 
 **Voice keying.** `MessageSender` was written to cover a voice keyer playing a
 recording, and nothing implements it. Each operator's recordings folder is