Black Box 39004, 39005 manual Description, 1.Key, Jumper, and Switch Settings, Setup

		CHAPTER 4: Setup
	Table 4-1. Key, Jumper, and Switch Settings
Number	Setting	Description
1		Loop Mode Key: Press the key switches through the
		following operating modes: Normal operation, Digital
		loop, Remote loop. The unit enters loop mode when the
		distant modem gets switched to remote loop.
2		Clock Source
		Internal
		Remote
		External
3		Interface Speed
	Position D	1.544 kbps
		1544
		All other settings are not applicable.
4
5		Processor Connector
		Not used. Do not install any jumpers!
6		For factory use only. Do not install any jumpers!
7		Fiber Optic Output Power
	Low
	High

11