In the log, you dial ZAP/4, which implies a single (analog?) line, but there is in the log a Hungup ‘Zap/4-1’, which seems to denote a channel with multiple ports, like a PRI line.
From http://www.voip-info.org/wiki/index.php?page=Asterisk+Zap+channels
chanspec: specifies which Zap channel or channel group, as defined in the configuration file, you want to use. It can be one of three types:
- one of the letters g, G, r, or R followed by a Zap channel group number. See “Dialing a Group”, below.
- for analog Zap interfaces: a simple channel number. Example: 1 means Zap channel 1.
- for PRI Zap interfaces: a span number, then a hyphen, then a port number. Example: 1-2 means Zap span 1, port 2.